<?xml version="1.0" encoding="US-ASCII"?>
<!--XBRL Document Created with Wdesk from Workiva-->
<!-- -->
<link:linkbase xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd" xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <link:roleRef roleURI="http://www.mastec.com/role/AccountsReceivableNetAndContractAssetsAndLiabilities" xlink:href="mtz-20180331.xsd#AccountsReceivableNetAndContractAssetsAndLiabilities" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/AccountsReceivableNetAndContractAssetsAndLiabilitiesNarrativeDetails" xlink:href="mtz-20180331.xsd#AccountsReceivableNetAndContractAssetsAndLiabilitiesNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/AccountsReceivableNetAndContractAssetsAndLiabilitiesScheduleOfAccountsReceivableNetAndContractAssetsAndLiabilitiesDetails" xlink:href="mtz-20180331.xsd#AccountsReceivableNetAndContractAssetsAndLiabilitiesScheduleOfAccountsReceivableNetAndContractAssetsAndLiabilitiesDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/AccountsReceivableNetAndContractAssetsAndLiabilitiesTables" xlink:href="mtz-20180331.xsd#AccountsReceivableNetAndContractAssetsAndLiabilitiesTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/BusinessBasisOfPresentationAndSignificantAccountingPolicies" xlink:href="mtz-20180331.xsd#BusinessBasisOfPresentationAndSignificantAccountingPolicies" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/BusinessBasisOfPresentationAndSignificantAccountingPoliciesNarrativeDetails" xlink:href="mtz-20180331.xsd#BusinessBasisOfPresentationAndSignificantAccountingPoliciesNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/BusinessBasisOfPresentationAndSignificantAccountingPoliciesPolicies" xlink:href="mtz-20180331.xsd#BusinessBasisOfPresentationAndSignificantAccountingPoliciesPolicies" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/BusinessBasisOfPresentationAndSignificantAccountingPoliciesRemainingPerformanceObligationsNarrativeDetails" xlink:href="mtz-20180331.xsd#BusinessBasisOfPresentationAndSignificantAccountingPoliciesRemainingPerformanceObligationsNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/CommitmentsAndContingencies" xlink:href="mtz-20180331.xsd#CommitmentsAndContingencies" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/CommitmentsAndContingenciesConcentrationsOfRiskNarrativeDetails" xlink:href="mtz-20180331.xsd#CommitmentsAndContingenciesConcentrationsOfRiskNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/CommitmentsAndContingenciesInvestmentArrangementsNarrativeDetails" xlink:href="mtz-20180331.xsd#CommitmentsAndContingenciesInvestmentArrangementsNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/CommitmentsAndContingenciesOtherCommitmentsAndContingenciesNarrativeDetails" xlink:href="mtz-20180331.xsd#CommitmentsAndContingenciesOtherCommitmentsAndContingenciesNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/CommitmentsAndContingenciesOtherGuaranteesNarrativeDetails" xlink:href="mtz-20180331.xsd#CommitmentsAndContingenciesOtherGuaranteesNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/CondensedUnauditedConsolidatedBalanceSheets" xlink:href="mtz-20180331.xsd#CondensedUnauditedConsolidatedBalanceSheets" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/CondensedUnauditedConsolidatedBalanceSheetsParenthetical" xlink:href="mtz-20180331.xsd#CondensedUnauditedConsolidatedBalanceSheetsParenthetical" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/CondensedUnauditedConsolidatedStatementsOfCashFlows" xlink:href="mtz-20180331.xsd#CondensedUnauditedConsolidatedStatementsOfCashFlows" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/CondensedUnauditedConsolidatedStatementsOfComprehensiveIncome" xlink:href="mtz-20180331.xsd#CondensedUnauditedConsolidatedStatementsOfComprehensiveIncome" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/CondensedUnauditedConsolidatedStatementsOfOperations" xlink:href="mtz-20180331.xsd#CondensedUnauditedConsolidatedStatementsOfOperations" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/Debt" xlink:href="mtz-20180331.xsd#Debt" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/DebtAdditionalInformationNarrativeDetails" xlink:href="mtz-20180331.xsd#DebtAdditionalInformationNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/DebtDebtGuaranteesAndCovenantsNarrativeDetails" xlink:href="mtz-20180331.xsd#DebtDebtGuaranteesAndCovenantsNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/DebtOtherCreditFacilitiesNarrativeDetails" xlink:href="mtz-20180331.xsd#DebtOtherCreditFacilitiesNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/DebtScheduleOfCarryingValuesOfDebtDetails" xlink:href="mtz-20180331.xsd#DebtScheduleOfCarryingValuesOfDebtDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/DebtSeniorSecuredCreditFacilityNarrativeDetails" xlink:href="mtz-20180331.xsd#DebtSeniorSecuredCreditFacilityNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/DebtTables" xlink:href="mtz-20180331.xsd#DebtTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/DocumentAndEntityInformation" xlink:href="mtz-20180331.xsd#DocumentAndEntityInformation" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/EarningsPerShare" xlink:href="mtz-20180331.xsd#EarningsPerShare" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/EarningsPerShareNarrativeDetails" xlink:href="mtz-20180331.xsd#EarningsPerShareNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/EarningsPerShareScheduleOfEarningsPerShareInformationDetails" xlink:href="mtz-20180331.xsd#EarningsPerShareScheduleOfEarningsPerShareInformationDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/EarningsPerShareTables" xlink:href="mtz-20180331.xsd#EarningsPerShareTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/Equity" xlink:href="mtz-20180331.xsd#Equity" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/EquityShareActivityNarrativeDetails" xlink:href="mtz-20180331.xsd#EquityShareActivityNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/FairValueOfFinancialInstruments" xlink:href="mtz-20180331.xsd#FairValueOfFinancialInstruments" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/FairValueOfFinancialInstrumentsAssetsAndLiabilitiesMeasuredAtFairValueOnNonRecurringBasisNarrativeDetails" xlink:href="mtz-20180331.xsd#FairValueOfFinancialInstrumentsAssetsAndLiabilitiesMeasuredAtFairValueOnNonRecurringBasisNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/FairValueOfFinancialInstrumentsAssetsAndLiabilitiesMeasuredAtFairValueOnRecurringBasisNarrativeDetails" xlink:href="mtz-20180331.xsd#FairValueOfFinancialInstrumentsAssetsAndLiabilitiesMeasuredAtFairValueOnRecurringBasisNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/FairValueOfFinancialInstrumentsEquityInvestmentsNarrativeDetails" xlink:href="mtz-20180331.xsd#FairValueOfFinancialInstrumentsEquityInvestmentsNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/FairValueOfFinancialInstrumentsOtherInvestmentsPacerNarrativeDetails" xlink:href="mtz-20180331.xsd#FairValueOfFinancialInstrumentsOtherInvestmentsPacerNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/FairValueOfFinancialInstrumentsOtherInvestmentsPensareNarrativeDetails" xlink:href="mtz-20180331.xsd#FairValueOfFinancialInstrumentsOtherInvestmentsPensareNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/FairValueOfFinancialInstrumentsTheWahaJvsNarrativeDetails" xlink:href="mtz-20180331.xsd#FairValueOfFinancialInstrumentsTheWahaJvsNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/GoodwillAndOtherIntangibleAssets" xlink:href="mtz-20180331.xsd#GoodwillAndOtherIntangibleAssets" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/GoodwillAndOtherIntangibleAssets2017AcquisitionsNarrativeDetails" xlink:href="mtz-20180331.xsd#GoodwillAndOtherIntangibleAssets2017AcquisitionsNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/GoodwillAndOtherIntangibleAssets2018AcquisitionsNarrativeDetails" xlink:href="mtz-20180331.xsd#GoodwillAndOtherIntangibleAssets2018AcquisitionsNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/GoodwillAndOtherIntangibleAssetsNarrativeDetails" xlink:href="mtz-20180331.xsd#GoodwillAndOtherIntangibleAssetsNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/GoodwillAndOtherIntangibleAssetsRollforwardOfOtherIntangibleAssetsDetails" xlink:href="mtz-20180331.xsd#GoodwillAndOtherIntangibleAssetsRollforwardOfOtherIntangibleAssetsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/GoodwillAndOtherIntangibleAssetsScheduleOfConsiderationPaidAndNetAssetsAcquiredBusinessCombinationsDetails" xlink:href="mtz-20180331.xsd#GoodwillAndOtherIntangibleAssetsScheduleOfConsiderationPaidAndNetAssetsAcquiredBusinessCombinationsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/GoodwillAndOtherIntangibleAssetsScheduleOfGoodwillBySegmentDetails" xlink:href="mtz-20180331.xsd#GoodwillAndOtherIntangibleAssetsScheduleOfGoodwillBySegmentDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/GoodwillAndOtherIntangibleAssetsTables" xlink:href="mtz-20180331.xsd#GoodwillAndOtherIntangibleAssetsTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/GoodwillAndOtherIntangibleAssetsUnauditedProFormaFinancialInformationNarrativeDetails" xlink:href="mtz-20180331.xsd#GoodwillAndOtherIntangibleAssetsUnauditedProFormaFinancialInformationNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/IncomeTaxes" xlink:href="mtz-20180331.xsd#IncomeTaxes" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/IncomeTaxesNarrativeDetails" xlink:href="mtz-20180331.xsd#IncomeTaxesNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/LeaseObligations" xlink:href="mtz-20180331.xsd#LeaseObligations" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/LeaseObligationsCapitalLeasesNarrativeDetails" xlink:href="mtz-20180331.xsd#LeaseObligationsCapitalLeasesNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/LeaseObligationsOperatingLeasesNarrativeDetails" xlink:href="mtz-20180331.xsd#LeaseObligationsOperatingLeasesNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/OtherRetirementPlans" xlink:href="mtz-20180331.xsd#OtherRetirementPlans" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/OtherRetirementPlansNarrativeDetails" xlink:href="mtz-20180331.xsd#OtherRetirementPlansNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/OtherRetirementPlansScheduleOfCoveredEmployeesAndContributionsMultiemployerPlansDetails" xlink:href="mtz-20180331.xsd#OtherRetirementPlansScheduleOfCoveredEmployeesAndContributionsMultiemployerPlansDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/OtherRetirementPlansTables" xlink:href="mtz-20180331.xsd#OtherRetirementPlansTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/PropertyAndEquipmentNet" xlink:href="mtz-20180331.xsd#PropertyAndEquipmentNet" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/PropertyAndEquipmentNetNarrativeDetails" xlink:href="mtz-20180331.xsd#PropertyAndEquipmentNetNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/PropertyAndEquipmentNetScheduleOfPropertyAndEquipmentNetDetails" xlink:href="mtz-20180331.xsd#PropertyAndEquipmentNetScheduleOfPropertyAndEquipmentNetDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/PropertyAndEquipmentNetTables" xlink:href="mtz-20180331.xsd#PropertyAndEquipmentNetTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/RelatedPartyTransactions" xlink:href="mtz-20180331.xsd#RelatedPartyTransactions" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/RelatedPartyTransactionsCciNarrativeDetails" xlink:href="mtz-20180331.xsd#RelatedPartyTransactionsCciNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/RelatedPartyTransactionsContractualJointVentureNarrativeDetails" xlink:href="mtz-20180331.xsd#RelatedPartyTransactionsContractualJointVentureNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/RelatedPartyTransactionsEquityMethodInvestmentNarrativeDetails" xlink:href="mtz-20180331.xsd#RelatedPartyTransactionsEquityMethodInvestmentNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/RelatedPartyTransactionsLeasesAndOtherTransactionsNarrativeDetails" xlink:href="mtz-20180331.xsd#RelatedPartyTransactionsLeasesAndOtherTransactionsNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/RelatedPartyTransactionsNonControllingInterestsNarrativeDetails" xlink:href="mtz-20180331.xsd#RelatedPartyTransactionsNonControllingInterestsNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/RelatedPartyTransactionsSplitDollarAgreementsNarrativeDetails" xlink:href="mtz-20180331.xsd#RelatedPartyTransactionsSplitDollarAgreementsNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/RelatedPartyTransactionsSubcontractingArrangementsAndOtherTransactionsNarrativeDetails" xlink:href="mtz-20180331.xsd#RelatedPartyTransactionsSubcontractingArrangementsAndOtherTransactionsNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/SegmentsAndRelatedInformation" xlink:href="mtz-20180331.xsd#SegmentsAndRelatedInformation" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/SegmentsAndRelatedInformationForeignOperationsNarrativeDetails" xlink:href="mtz-20180331.xsd#SegmentsAndRelatedInformationForeignOperationsNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/SegmentsAndRelatedInformationNarrativeDetails" xlink:href="mtz-20180331.xsd#SegmentsAndRelatedInformationNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/SegmentsAndRelatedInformationReconciliationOfConsolidatedIncomeBeforeIncomeTaxesToEbitdaDetails" xlink:href="mtz-20180331.xsd#SegmentsAndRelatedInformationReconciliationOfConsolidatedIncomeBeforeIncomeTaxesToEbitdaDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/SegmentsAndRelatedInformationScheduleOfFinancialInformationByReportableSegmentDepreciationAndAmortizationDetails" xlink:href="mtz-20180331.xsd#SegmentsAndRelatedInformationScheduleOfFinancialInformationByReportableSegmentDepreciationAndAmortizationDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/SegmentsAndRelatedInformationScheduleOfFinancialInformationByReportableSegmentEbitdaDetails" xlink:href="mtz-20180331.xsd#SegmentsAndRelatedInformationScheduleOfFinancialInformationByReportableSegmentEbitdaDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/SegmentsAndRelatedInformationScheduleOfFinancialInformationByReportableSegmentRevenueDetails" xlink:href="mtz-20180331.xsd#SegmentsAndRelatedInformationScheduleOfFinancialInformationByReportableSegmentRevenueDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/SegmentsAndRelatedInformationScheduleOfSignificantCustomersRevenueConcentrationInformationDetails" xlink:href="mtz-20180331.xsd#SegmentsAndRelatedInformationScheduleOfSignificantCustomersRevenueConcentrationInformationDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/SegmentsAndRelatedInformationTables" xlink:href="mtz-20180331.xsd#SegmentsAndRelatedInformationTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/StockBasedCompensationAndOtherEmployeeBenefitPlans" xlink:href="mtz-20180331.xsd#StockBasedCompensationAndOtherEmployeeBenefitPlans" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/StockBasedCompensationAndOtherEmployeeBenefitPlansEmployeeStockPurchasePlansNarrativeDetails" xlink:href="mtz-20180331.xsd#StockBasedCompensationAndOtherEmployeeBenefitPlansEmployeeStockPurchasePlansNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/StockBasedCompensationAndOtherEmployeeBenefitPlansNarrativeDetails" xlink:href="mtz-20180331.xsd#StockBasedCompensationAndOtherEmployeeBenefitPlansNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/StockBasedCompensationAndOtherEmployeeBenefitPlansRestrictedSharesNarrativeDetails" xlink:href="mtz-20180331.xsd#StockBasedCompensationAndOtherEmployeeBenefitPlansRestrictedSharesNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/StockBasedCompensationAndOtherEmployeeBenefitPlansScheduleOfActivityEmployeeStockPurchasePlansDetails" xlink:href="mtz-20180331.xsd#StockBasedCompensationAndOtherEmployeeBenefitPlansScheduleOfActivityEmployeeStockPurchasePlansDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/StockBasedCompensationAndOtherEmployeeBenefitPlansScheduleOfActivityRestrictedSharesDetails" xlink:href="mtz-20180331.xsd#StockBasedCompensationAndOtherEmployeeBenefitPlansScheduleOfActivityRestrictedSharesDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/StockBasedCompensationAndOtherEmployeeBenefitPlansScheduleOfNonCashStockBasedCompensationExpenseAndRelatedTaxEffectsDetails" xlink:href="mtz-20180331.xsd#StockBasedCompensationAndOtherEmployeeBenefitPlansScheduleOfNonCashStockBasedCompensationExpenseAndRelatedTaxEffectsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/StockBasedCompensationAndOtherEmployeeBenefitPlansTables" xlink:href="mtz-20180331.xsd#StockBasedCompensationAndOtherEmployeeBenefitPlansTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/SupplementalGuarantorFinancialInformation" xlink:href="mtz-20180331.xsd#SupplementalGuarantorFinancialInformation" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/SupplementalGuarantorFinancialInformationCondensedUnauditedConsolidatingBalanceSheetsDetails" xlink:href="mtz-20180331.xsd#SupplementalGuarantorFinancialInformationCondensedUnauditedConsolidatingBalanceSheetsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/SupplementalGuarantorFinancialInformationCondensedUnauditedConsolidatingStatementsOfCashFlowsDetails" xlink:href="mtz-20180331.xsd#SupplementalGuarantorFinancialInformationCondensedUnauditedConsolidatingStatementsOfCashFlowsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/SupplementalGuarantorFinancialInformationCondensedUnauditedConsolidatingStatementsOfOperationsAndComprehensiveIncomeLossDetails" xlink:href="mtz-20180331.xsd#SupplementalGuarantorFinancialInformationCondensedUnauditedConsolidatingStatementsOfOperationsAndComprehensiveIncomeLossDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/SupplementalGuarantorFinancialInformationNarrativeDetails" xlink:href="mtz-20180331.xsd#SupplementalGuarantorFinancialInformationNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.mastec.com/role/SupplementalGuarantorFinancialInformationTables" xlink:href="mtz-20180331.xsd#SupplementalGuarantorFinancialInformationTables" xlink:type="simple" />
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all" xlink:type="simple" />
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default" xlink:type="simple" />
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain" xlink:type="simple" />
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member" xlink:type="simple" />
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension" xlink:type="simple" />
  <link:definitionLink xlink:role="http://www.mastec.com/role/AccountsReceivableNetAndContractAssetsAndLiabilities" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.mastec.com/role/AccountsReceivableNetAndContractAssetsAndLiabilitiesNarrativeDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AccountsNotesAndLoansReceivableLineItems" xlink:label="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_72A0E4C10120980BB6F614067D6DAE03" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable" xlink:label="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_9FE9E4A1C3D022E6B8E514067D6C2C76" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_72A0E4C10120980BB6F614067D6DAE03" xlink:to="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_9FE9E4A1C3D022E6B8E514067D6C2C76" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RangeAxis" xlink:label="loc_us-gaap_RangeAxis_BED6E30B74B2D8AF67B014067D6CDFAB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_9FE9E4A1C3D022E6B8E514067D6C2C76" xlink:to="loc_us-gaap_RangeAxis_BED6E30B74B2D8AF67B014067D6CDFAB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RangeMember" xlink:label="loc_us-gaap_RangeMember_BE6FF531137E529D895E14067D6CB825_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RangeAxis_BED6E30B74B2D8AF67B014067D6CDFAB" xlink:to="loc_us-gaap_RangeMember_BE6FF531137E529D895E14067D6CB825_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RangeMember" xlink:label="loc_us-gaap_RangeMember_BE6FF531137E529D895E14067D6CB825" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RangeAxis_BED6E30B74B2D8AF67B014067D6CDFAB" xlink:to="loc_us-gaap_RangeMember_BE6FF531137E529D895E14067D6CB825" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_MinimumMember" xlink:label="loc_us-gaap_MinimumMember_12F4042E18F75E8C6C7314067D6D036C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RangeMember_BE6FF531137E529D895E14067D6CB825" xlink:to="loc_us-gaap_MinimumMember_12F4042E18F75E8C6C7314067D6D036C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_MaximumMember" xlink:label="loc_us-gaap_MaximumMember_0252F8555842A5C784F014067D6D4779" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RangeMember_BE6FF531137E529D895E14067D6CB825" xlink:to="loc_us-gaap_MaximumMember_0252F8555842A5C784F014067D6D4779" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncomeStatementLocationAxis" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_8861FA16B56E07B7139714067D6D020D" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_9FE9E4A1C3D022E6B8E514067D6C2C76" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_8861FA16B56E07B7139714067D6D020D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_B9631567F4FD2DF197EB14067D6D0022_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_8861FA16B56E07B7139714067D6D020D" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_B9631567F4FD2DF197EB14067D6D0022_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_B9631567F4FD2DF197EB14067D6D0022" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_8861FA16B56E07B7139714067D6D020D" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_B9631567F4FD2DF197EB14067D6D0022" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_InterestExpenseMember" xlink:label="loc_us-gaap_InterestExpenseMember_0B7872E0C675C5380F2A14067D6DE657" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_B9631567F4FD2DF197EB14067D6D0022" xlink:to="loc_us-gaap_InterestExpenseMember_0B7872E0C675C5380F2A14067D6DE657" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis" xlink:label="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_09E5290DEB597623A2D814067D6D3027" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_9FE9E4A1C3D022E6B8E514067D6C2C76" xlink:to="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_09E5290DEB597623A2D814067D6D3027" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ReceivableTypeDomain" xlink:label="loc_us-gaap_ReceivableTypeDomain_490EBAC49ADF780D181F14067D6DBB6F_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_09E5290DEB597623A2D814067D6D3027" xlink:to="loc_us-gaap_ReceivableTypeDomain_490EBAC49ADF780D181F14067D6DBB6F_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ReceivableTypeDomain" xlink:label="loc_us-gaap_ReceivableTypeDomain_490EBAC49ADF780D181F14067D6DBB6F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_09E5290DEB597623A2D814067D6D3027" xlink:to="loc_us-gaap_ReceivableTypeDomain_490EBAC49ADF780D181F14067D6DBB6F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FinanceReceivablesMember" xlink:label="loc_us-gaap_FinanceReceivablesMember_A5083044E0A4B60E696114067D6DC05E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReceivableTypeDomain_490EBAC49ADF780D181F14067D6DBB6F" xlink:to="loc_us-gaap_FinanceReceivablesMember_A5083044E0A4B60E696114067D6DC05E" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_RetainagePercentOfContractBillings" xlink:label="loc_mtz_RetainagePercentOfContractBillings_EFE59531F1615572695B14067D6D2E76" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_72A0E4C10120980BB6F614067D6DAE03" xlink:to="loc_mtz_RetainagePercentOfContractBillings_EFE59531F1615572695B14067D6D2E76" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ContractWithCustomerLiabilityRevenueRecognized" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityRevenueRecognized_ADA1B5839463BF1537CD14067D6D50AC" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_72A0E4C10120980BB6F614067D6DAE03" xlink:to="loc_us-gaap_ContractWithCustomerLiabilityRevenueRecognized_ADA1B5839463BF1537CD14067D6D50AC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ProvisionForDoubtfulAccounts" xlink:label="loc_us-gaap_ProvisionForDoubtfulAccounts_F532435E70584B46A58114067D6DB1C9" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_72A0E4C10120980BB6F614067D6DAE03" xlink:to="loc_us-gaap_ProvisionForDoubtfulAccounts_F532435E70584B46A58114067D6DB1C9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_GainLossOnSaleOfAccountsReceivable" xlink:label="loc_us-gaap_GainLossOnSaleOfAccountsReceivable_A5FED7079F3A54057E7D14067D6D8F7C" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_72A0E4C10120980BB6F614067D6DAE03" xlink:to="loc_us-gaap_GainLossOnSaleOfAccountsReceivable_A5FED7079F3A54057E7D14067D6D8F7C" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.mastec.com/role/AccountsReceivableNetAndContractAssetsAndLiabilitiesScheduleOfAccountsReceivableNetAndContractAssetsAndLiabilitiesDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.mastec.com/role/AccountsReceivableNetAndContractAssetsAndLiabilitiesTables" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AccountsNotesAndLoansReceivableLineItems" xlink:label="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_F101ABFBE31D25D49F4D0F8209E7CDEC" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable" xlink:label="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_E5CE814A90384456F6290F8209E707D5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_F101ABFBE31D25D49F4D0F8209E7CDEC" xlink:to="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_E5CE814A90384456F6290F8209E707D5" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis" xlink:label="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_00305C185DFC0314FC350F8209E75B21" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_E5CE814A90384456F6290F8209E707D5" xlink:to="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_00305C185DFC0314FC350F8209E75B21" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ReceivableTypeDomain" xlink:label="loc_us-gaap_ReceivableTypeDomain_BA7A82CEFB7E50A626470F8209E7102C_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_00305C185DFC0314FC350F8209E75B21" xlink:to="loc_us-gaap_ReceivableTypeDomain_BA7A82CEFB7E50A626470F8209E7102C_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ReceivableTypeDomain" xlink:label="loc_us-gaap_ReceivableTypeDomain_BA7A82CEFB7E50A626470F8209E7102C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_00305C185DFC0314FC350F8209E75B21" xlink:to="loc_us-gaap_ReceivableTypeDomain_BA7A82CEFB7E50A626470F8209E7102C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_TradeAccountsReceivableMember" xlink:label="loc_us-gaap_TradeAccountsReceivableMember_5C48E35D671A829F290A0F8209E7A5B8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReceivableTypeDomain_BA7A82CEFB7E50A626470F8209E7102C" xlink:to="loc_us-gaap_TradeAccountsReceivableMember_5C48E35D671A829F290A0F8209E7A5B8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTextBlock" xlink:label="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTextBlock_CB594EAFA37D7EE754C50F8209E81391" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_F101ABFBE31D25D49F4D0F8209E7CDEC" xlink:to="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTextBlock_CB594EAFA37D7EE754C50F8209E81391" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.mastec.com/role/BusinessBasisOfPresentationAndSignificantAccountingPolicies" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.mastec.com/role/BusinessBasisOfPresentationAndSignificantAccountingPoliciesNarrativeDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DisaggregationOfRevenueLineItems" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_0A2665DE15AEE3AF0A7116F9E1C0D2AF" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DisaggregationOfRevenueTable" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_2741F2EE474C3F10D02E16F9E1BEF190" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_0A2665DE15AEE3AF0A7116F9E1C0D2AF" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_2741F2EE474C3F10D02E16F9E1BEF190" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AdjustmentsForNewAccountingPronouncementsAxis" xlink:label="loc_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_E58940952265602433AB16F9E1BE7D09" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_2741F2EE474C3F10D02E16F9E1BEF190" xlink:to="loc_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_E58940952265602433AB16F9E1BE7D09" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_TypeOfAdoptionMember" xlink:label="loc_us-gaap_TypeOfAdoptionMember_A890B4842CB632792E4616F9E1BEEE64_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_E58940952265602433AB16F9E1BE7D09" xlink:to="loc_us-gaap_TypeOfAdoptionMember_A890B4842CB632792E4616F9E1BEEE64_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_TypeOfAdoptionMember" xlink:label="loc_us-gaap_TypeOfAdoptionMember_A890B4842CB632792E4616F9E1BEEE64" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_E58940952265602433AB16F9E1BE7D09" xlink:to="loc_us-gaap_TypeOfAdoptionMember_A890B4842CB632792E4616F9E1BEEE64" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AccountingStandardsUpdate201409Member" xlink:label="loc_us-gaap_AccountingStandardsUpdate201409Member_49483B2BE73068D82CE416F9E1BE31DC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TypeOfAdoptionMember_A890B4842CB632792E4616F9E1BEEE64" xlink:to="loc_us-gaap_AccountingStandardsUpdate201409Member_49483B2BE73068D82CE416F9E1BE31DC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AccountingStandardsUpdate201615Member" xlink:label="loc_us-gaap_AccountingStandardsUpdate201615Member_5790D4D46D66043D9E8116F9E1BF3C9E" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TypeOfAdoptionMember_A890B4842CB632792E4616F9E1BEEE64" xlink:to="loc_us-gaap_AccountingStandardsUpdate201615Member_5790D4D46D66043D9E8116F9E1BF3C9E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_InitialApplicationPeriodCumulativeEffectTransitionAxis" xlink:label="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionAxis_58251BF2C68E98F0698C16F9E1BFCD95" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_2741F2EE474C3F10D02E16F9E1BEF190" xlink:to="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionAxis_58251BF2C68E98F0698C16F9E1BFCD95" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_InitialApplicationPeriodCumulativeEffectTransitionDomain" xlink:label="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionDomain_A1AE7046A0C73700F00816F9E1BF78F8_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionAxis_58251BF2C68E98F0698C16F9E1BFCD95" xlink:to="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionDomain_A1AE7046A0C73700F00816F9E1BF78F8_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_InitialApplicationPeriodCumulativeEffectTransitionDomain" xlink:label="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionDomain_A1AE7046A0C73700F00816F9E1BF78F8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionAxis_58251BF2C68E98F0698C16F9E1BFCD95" xlink:to="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionDomain_A1AE7046A0C73700F00816F9E1BF78F8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DifferenceBetweenRevenueGuidanceInEffectBeforeAndAfterTopic606Member" xlink:label="loc_us-gaap_DifferenceBetweenRevenueGuidanceInEffectBeforeAndAfterTopic606Member_4C37ED0F6FB63D9A836116F9E1BF5C2D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionDomain_A1AE7046A0C73700F00816F9E1BF78F8" xlink:to="loc_us-gaap_DifferenceBetweenRevenueGuidanceInEffectBeforeAndAfterTopic606Member_4C37ED0F6FB63D9A836116F9E1BF5C2D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConcentrationRiskByBenchmarkAxis" xlink:label="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_367C539A45453A4A78D516F9E1BF61CD" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_2741F2EE474C3F10D02E16F9E1BEF190" xlink:to="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_367C539A45453A4A78D516F9E1BF61CD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConcentrationRiskBenchmarkDomain" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_1ABE9EC1D3331D68002A16F9E1BF6D4C_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_367C539A45453A4A78D516F9E1BF61CD" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_1ABE9EC1D3331D68002A16F9E1BF6D4C_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConcentrationRiskBenchmarkDomain" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_1ABE9EC1D3331D68002A16F9E1BF6D4C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_367C539A45453A4A78D516F9E1BF61CD" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_1ABE9EC1D3331D68002A16F9E1BF6D4C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SalesRevenueServicesNetMember" xlink:label="loc_us-gaap_SalesRevenueServicesNetMember_06FD0C2E5B6CA5EA603916F9E1BF6945" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_1ABE9EC1D3331D68002A16F9E1BF6D4C" xlink:to="loc_us-gaap_SalesRevenueServicesNetMember_06FD0C2E5B6CA5EA603916F9E1BF6945" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConcentrationRiskByTypeAxis" xlink:label="loc_us-gaap_ConcentrationRiskByTypeAxis_287B4864085C19C4ED8216F9E1BF70B3" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_2741F2EE474C3F10D02E16F9E1BEF190" xlink:to="loc_us-gaap_ConcentrationRiskByTypeAxis_287B4864085C19C4ED8216F9E1BF70B3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConcentrationRiskTypeDomain" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_9BDCEFFD26F8568F99E716F9E1BFA395_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_287B4864085C19C4ED8216F9E1BF70B3" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_9BDCEFFD26F8568F99E716F9E1BFA395_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConcentrationRiskTypeDomain" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_9BDCEFFD26F8568F99E716F9E1BFA395" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_287B4864085C19C4ED8216F9E1BF70B3" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_9BDCEFFD26F8568F99E716F9E1BFA395" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ProductConcentrationRiskMember" xlink:label="loc_us-gaap_ProductConcentrationRiskMember_AB5C9955647769FEB0B716F9E1BF4D68" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_9BDCEFFD26F8568F99E716F9E1BFA395" xlink:to="loc_us-gaap_ProductConcentrationRiskMember_AB5C9955647769FEB0B716F9E1BF4D68" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ProductOrServiceAxis" xlink:label="loc_us-gaap_ProductOrServiceAxis_4D10BA1F3749B6D05CA416F9E1BF9139" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_2741F2EE474C3F10D02E16F9E1BEF190" xlink:to="loc_us-gaap_ProductOrServiceAxis_4D10BA1F3749B6D05CA416F9E1BF9139" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ProductsAndServicesDomain" xlink:label="loc_us-gaap_ProductsAndServicesDomain_5DC7059CEB96A49431EB16F9E1BFD587_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ProductOrServiceAxis_4D10BA1F3749B6D05CA416F9E1BF9139" xlink:to="loc_us-gaap_ProductsAndServicesDomain_5DC7059CEB96A49431EB16F9E1BFD587_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ProductsAndServicesDomain" xlink:label="loc_us-gaap_ProductsAndServicesDomain_5DC7059CEB96A49431EB16F9E1BFD587" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ProductOrServiceAxis_4D10BA1F3749B6D05CA416F9E1BF9139" xlink:to="loc_us-gaap_ProductsAndServicesDomain_5DC7059CEB96A49431EB16F9E1BFD587" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_MasterServiceAndOtherServiceAgreementsMember" xlink:label="loc_mtz_MasterServiceAndOtherServiceAgreementsMember_8B9852B1E1FD20075A7D16F9E1C0AE3D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ProductsAndServicesDomain_5DC7059CEB96A49431EB16F9E1BFD587" xlink:to="loc_mtz_MasterServiceAndOtherServiceAgreementsMember_8B9852B1E1FD20075A7D16F9E1C0AE3D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RangeAxis" xlink:label="loc_us-gaap_RangeAxis_64E0233B0966AE06314A16F9E1C03DE9" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_2741F2EE474C3F10D02E16F9E1BEF190" xlink:to="loc_us-gaap_RangeAxis_64E0233B0966AE06314A16F9E1C03DE9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RangeMember" xlink:label="loc_us-gaap_RangeMember_D7567BD6E28E18078D9616F9E1C024D9_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RangeAxis_64E0233B0966AE06314A16F9E1C03DE9" xlink:to="loc_us-gaap_RangeMember_D7567BD6E28E18078D9616F9E1C024D9_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RangeMember" xlink:label="loc_us-gaap_RangeMember_D7567BD6E28E18078D9616F9E1C024D9" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RangeAxis_64E0233B0966AE06314A16F9E1C03DE9" xlink:to="loc_us-gaap_RangeMember_D7567BD6E28E18078D9616F9E1C024D9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_MaximumMember" xlink:label="loc_us-gaap_MaximumMember_A3768EDFF9F8FC9FC5F116F9E1C0A7C4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RangeMember_D7567BD6E28E18078D9616F9E1C024D9" xlink:to="loc_us-gaap_MaximumMember_A3768EDFF9F8FC9FC5F116F9E1C0A7C4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_StatementScenarioAxis" xlink:label="loc_us-gaap_StatementScenarioAxis_E4A0F428C5EAA1EAAAB516F9E1C0A77D" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_2741F2EE474C3F10D02E16F9E1BEF190" xlink:to="loc_us-gaap_StatementScenarioAxis_E4A0F428C5EAA1EAAAB516F9E1C0A77D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScenarioUnspecifiedDomain" xlink:label="loc_us-gaap_ScenarioUnspecifiedDomain_C56623C983725A80ADAD16F9E1C0B261_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementScenarioAxis_E4A0F428C5EAA1EAAAB516F9E1C0A77D" xlink:to="loc_us-gaap_ScenarioUnspecifiedDomain_C56623C983725A80ADAD16F9E1C0B261_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScenarioUnspecifiedDomain" xlink:label="loc_us-gaap_ScenarioUnspecifiedDomain_C56623C983725A80ADAD16F9E1C0B261" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementScenarioAxis_E4A0F428C5EAA1EAAAB516F9E1C0A77D" xlink:to="loc_us-gaap_ScenarioUnspecifiedDomain_C56623C983725A80ADAD16F9E1C0B261" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScenarioPlanMember" xlink:label="loc_us-gaap_ScenarioPlanMember_E1DBEF9397572656024316F9E1C0C680" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScenarioUnspecifiedDomain_C56623C983725A80ADAD16F9E1C0B261" xlink:to="loc_us-gaap_ScenarioPlanMember_E1DBEF9397572656024316F9E1C0C680" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ProFormaMember" xlink:label="loc_us-gaap_ProFormaMember_6AA5FE2EF575D807444F16F9E1C024C1" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScenarioUnspecifiedDomain_C56623C983725A80ADAD16F9E1C0B261" xlink:to="loc_us-gaap_ProFormaMember_6AA5FE2EF575D807444F16F9E1C024C1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RetainedEarningsAccumulatedDeficit" xlink:label="loc_us-gaap_RetainedEarningsAccumulatedDeficit_B97ACC8EDC24F0B83C0916F9E1C197D6" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_0A2665DE15AEE3AF0A7116F9E1C0D2AF" xlink:to="loc_us-gaap_RetainedEarningsAccumulatedDeficit_B97ACC8EDC24F0B83C0916F9E1C197D6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConcentrationRiskPercentage1" xlink:label="loc_us-gaap_ConcentrationRiskPercentage1_75DD6D9B37EE9C2A74A516F9E1C16D39" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_0A2665DE15AEE3AF0A7116F9E1C0D2AF" xlink:to="loc_us-gaap_ConcentrationRiskPercentage1_75DD6D9B37EE9C2A74A516F9E1C16D39" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ContractWithCustomerPerformanceObligationSatisfiedInPreviousPeriod" xlink:label="loc_us-gaap_ContractWithCustomerPerformanceObligationSatisfiedInPreviousPeriod_984F6B8242406AAA667416F9E1C1ECFD" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_0A2665DE15AEE3AF0A7116F9E1C0D2AF" xlink:to="loc_us-gaap_ContractWithCustomerPerformanceObligationSatisfiedInPreviousPeriod_984F6B8242406AAA667416F9E1C1ECFD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ContractsReceivableClaimsAndUncertainAmountsExpectedToBeCollectedWithinOneYear" xlink:label="loc_us-gaap_ContractsReceivableClaimsAndUncertainAmountsExpectedToBeCollectedWithinOneYear_479AA6E49314A52C7F0716F9E1C1BD1F" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_0A2665DE15AEE3AF0A7116F9E1C0D2AF" xlink:to="loc_us-gaap_ContractsReceivableClaimsAndUncertainAmountsExpectedToBeCollectedWithinOneYear_479AA6E49314A52C7F0716F9E1C1BD1F" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_UnapprovedChangeOrdersAndOrClaimsExpectedTermForApproval" xlink:label="loc_mtz_UnapprovedChangeOrdersAndOrClaimsExpectedTermForApproval_075B435F9EAB7F58577216F9E1C199CB" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_0A2665DE15AEE3AF0A7116F9E1C0D2AF" xlink:to="loc_mtz_UnapprovedChangeOrdersAndOrClaimsExpectedTermForApproval_075B435F9EAB7F58577216F9E1C199CB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod_6DDEFCF47AAA5C6E31C816F9E1C13CF6" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_0A2665DE15AEE3AF0A7116F9E1C0D2AF" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod_6DDEFCF47AAA5C6E31C816F9E1C13CF6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PaymentForContingentConsiderationLiabilityOperatingActivities" xlink:label="loc_us-gaap_PaymentForContingentConsiderationLiabilityOperatingActivities_715A76BF8E3BFBEA08FC16F9E1C19490" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_0A2665DE15AEE3AF0A7116F9E1C0D2AF" xlink:to="loc_us-gaap_PaymentForContingentConsiderationLiabilityOperatingActivities_715A76BF8E3BFBEA08FC16F9E1C19490" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.mastec.com/role/BusinessBasisOfPresentationAndSignificantAccountingPoliciesPolicies" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.mastec.com/role/BusinessBasisOfPresentationAndSignificantAccountingPoliciesRemainingPerformanceObligationsNarrativeDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_F5E694589B08A7EEDD131767EE9507AA" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_0DFDB726D328AEC51B271767EE950D49" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_F5E694589B08A7EEDD131767EE9507AA" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_0DFDB726D328AEC51B271767EE950D49" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_CFA60633A3D87F6DD1021767EE950113" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_0DFDB726D328AEC51B271767EE950D49" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_CFA60633A3D87F6DD1021767EE950113" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RevenueRemainingPerformanceObligation" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligation_EB8AF41B10C98331D9161767EE959D79" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_F5E694589B08A7EEDD131767EE9507AA" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligation_EB8AF41B10C98331D9161767EE959D79" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod_CC8672EE63821EDCFE021767EE959A1F" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_F5E694589B08A7EEDD131767EE9507AA" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod_CC8672EE63821EDCFE021767EE959A1F" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.mastec.com/role/CommitmentsAndContingencies" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.mastec.com/role/CommitmentsAndContingenciesConcentrationsOfRiskNarrativeDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConcentrationRiskLineItems" xlink:label="loc_us-gaap_ConcentrationRiskLineItems_275290DBFF4EE7E6299D62AD001AB838" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConcentrationRiskTable" xlink:label="loc_us-gaap_ConcentrationRiskTable_00A12D57DFC48D02259B62AD0019F471" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_275290DBFF4EE7E6299D62AD001AB838" xlink:to="loc_us-gaap_ConcentrationRiskTable_00A12D57DFC48D02259B62AD0019F471" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConcentrationRiskByBenchmarkAxis" xlink:label="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_15DD1E500E5AF41E604862AD00191C2D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConcentrationRiskTable_00A12D57DFC48D02259B62AD0019F471" xlink:to="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_15DD1E500E5AF41E604862AD00191C2D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConcentrationRiskBenchmarkDomain" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_274D8727FE507DCCC02962AD0019301C_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_15DD1E500E5AF41E604862AD00191C2D" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_274D8727FE507DCCC02962AD0019301C_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConcentrationRiskBenchmarkDomain" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_274D8727FE507DCCC02962AD0019301C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_15DD1E500E5AF41E604862AD00191C2D" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_274D8727FE507DCCC02962AD0019301C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AccountsReceivableMember" xlink:label="loc_us-gaap_AccountsReceivableMember_D0A619365A78676103E262AD00197BAD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_274D8727FE507DCCC02962AD0019301C" xlink:to="loc_us-gaap_AccountsReceivableMember_D0A619365A78676103E262AD00197BAD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SalesRevenueServicesNetMember" xlink:label="loc_us-gaap_SalesRevenueServicesNetMember_B2BFD07AA669043846EC62AD0019D345" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_274D8727FE507DCCC02962AD0019301C" xlink:to="loc_us-gaap_SalesRevenueServicesNetMember_B2BFD07AA669043846EC62AD0019D345" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConcentrationRiskByTypeAxis" xlink:label="loc_us-gaap_ConcentrationRiskByTypeAxis_F06DAC83334D95550F6162AD0019CEBC" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConcentrationRiskTable_00A12D57DFC48D02259B62AD0019F471" xlink:to="loc_us-gaap_ConcentrationRiskByTypeAxis_F06DAC83334D95550F6162AD0019CEBC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConcentrationRiskTypeDomain" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_88D0106363C44F951CC362AD001AEF86_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_F06DAC83334D95550F6162AD0019CEBC" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_88D0106363C44F951CC362AD001AEF86_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConcentrationRiskTypeDomain" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_88D0106363C44F951CC362AD001AEF86" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_F06DAC83334D95550F6162AD0019CEBC" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_88D0106363C44F951CC362AD001AEF86" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CreditConcentrationRiskMember" xlink:label="loc_us-gaap_CreditConcentrationRiskMember_72B99865C6243AC2B00862AD001A8089" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_88D0106363C44F951CC362AD001AEF86" xlink:to="loc_us-gaap_CreditConcentrationRiskMember_72B99865C6243AC2B00862AD001A8089" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CustomerConcentrationRiskMember" xlink:label="loc_us-gaap_CustomerConcentrationRiskMember_227A441872294070378B62AD001A02AB" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_88D0106363C44F951CC362AD001AEF86" xlink:to="loc_us-gaap_CustomerConcentrationRiskMember_227A441872294070378B62AD001A02AB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_MajorCustomersAxis" xlink:label="loc_us-gaap_MajorCustomersAxis_1C9FBDE3B3B510C00BB662AD001AF8FB" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConcentrationRiskTable_00A12D57DFC48D02259B62AD0019F471" xlink:to="loc_us-gaap_MajorCustomersAxis_1C9FBDE3B3B510C00BB662AD001AF8FB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NameOfMajorCustomerDomain" xlink:label="loc_us-gaap_NameOfMajorCustomerDomain_B2D5485302BE05E9130C62AD001A66E8_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_MajorCustomersAxis_1C9FBDE3B3B510C00BB662AD001AF8FB" xlink:to="loc_us-gaap_NameOfMajorCustomerDomain_B2D5485302BE05E9130C62AD001A66E8_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NameOfMajorCustomerDomain" xlink:label="loc_us-gaap_NameOfMajorCustomerDomain_B2D5485302BE05E9130C62AD001A66E8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_MajorCustomersAxis_1C9FBDE3B3B510C00BB662AD001AF8FB" xlink:to="loc_us-gaap_NameOfMajorCustomerDomain_B2D5485302BE05E9130C62AD001A66E8" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_CustomerWithHighestNetAccountsReceivablePosition1Member" xlink:label="loc_mtz_CustomerWithHighestNetAccountsReceivablePosition1Member_904AAD0E267C21E4696262AD001AEC31" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NameOfMajorCustomerDomain_B2D5485302BE05E9130C62AD001A66E8" xlink:to="loc_mtz_CustomerWithHighestNetAccountsReceivablePosition1Member_904AAD0E267C21E4696262AD001AEC31" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_CustomerWithSecondHighestNetAccountsReceivablePositionMember" xlink:label="loc_mtz_CustomerWithSecondHighestNetAccountsReceivablePositionMember_E769BCDC049511DFB73562AD001AFF39" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NameOfMajorCustomerDomain_B2D5485302BE05E9130C62AD001A66E8" xlink:to="loc_mtz_CustomerWithSecondHighestNetAccountsReceivablePositionMember_E769BCDC049511DFB73562AD001AFF39" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_TenLargestCustomers1Member" xlink:label="loc_mtz_TenLargestCustomers1Member_EEEFBE6FCD876D85BF0962AD001AD75B" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NameOfMajorCustomerDomain_B2D5485302BE05E9130C62AD001A66E8" xlink:to="loc_mtz_TenLargestCustomers1Member_EEEFBE6FCD876D85BF0962AD001AD75B" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_NumberOfCustomers1" xlink:label="loc_mtz_NumberOfCustomers1_E1C2993EDC20AFE654B662AD001A1411" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_275290DBFF4EE7E6299D62AD001AB838" xlink:to="loc_mtz_NumberOfCustomers1_E1C2993EDC20AFE654B662AD001A1411" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConcentrationRiskPercentage1" xlink:label="loc_us-gaap_ConcentrationRiskPercentage1_4DFF612CB99D580554C362AD001AF719" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_275290DBFF4EE7E6299D62AD001AB838" xlink:to="loc_us-gaap_ConcentrationRiskPercentage1_4DFF612CB99D580554C362AD001AF719" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.mastec.com/role/CommitmentsAndContingenciesInvestmentArrangementsNarrativeDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_OtherCommitmentsLineItems" xlink:label="loc_us-gaap_OtherCommitmentsLineItems_CF0D148DC22E854A3342121B941241B7" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_OtherCommitmentsTable" xlink:label="loc_us-gaap_OtherCommitmentsTable_6516888D8A101B3F324D121B9411CAB4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_OtherCommitmentsLineItems_CF0D148DC22E854A3342121B941241B7" xlink:to="loc_us-gaap_OtherCommitmentsTable_6516888D8A101B3F324D121B9411CAB4" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_F19C827DFEFFFA48A8E4121B94117498" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_OtherCommitmentsTable_6516888D8A101B3F324D121B9411CAB4" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_F19C827DFEFFFA48A8E4121B94117498" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_EBAAEF97EC737996A138121B94115040_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_F19C827DFEFFFA48A8E4121B94117498" xlink:to="loc_us-gaap_RelatedPartyDomain_EBAAEF97EC737996A138121B94115040_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_EBAAEF97EC737996A138121B94115040" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_F19C827DFEFFFA48A8E4121B94117498" xlink:to="loc_us-gaap_RelatedPartyDomain_EBAAEF97EC737996A138121B94115040" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CorporateJointVentureMember" xlink:label="loc_us-gaap_CorporateJointVentureMember_511E8BE99DF80B6E4343121B94116CBF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_EBAAEF97EC737996A138121B94115040" xlink:to="loc_us-gaap_CorporateJointVentureMember_511E8BE99DF80B6E4343121B94116CBF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_OwnershipAxis" xlink:label="loc_us-gaap_OwnershipAxis_BC89AD353898DE1FE2A6121B94110BD8" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_OtherCommitmentsTable_6516888D8A101B3F324D121B9411CAB4" xlink:to="loc_us-gaap_OwnershipAxis_BC89AD353898DE1FE2A6121B94110BD8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_OwnershipDomain" xlink:label="loc_us-gaap_OwnershipDomain_7A871FE7E765C5605A52121B9411A23E_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_OwnershipAxis_BC89AD353898DE1FE2A6121B94110BD8" xlink:to="loc_us-gaap_OwnershipDomain_7A871FE7E765C5605A52121B9411A23E_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_OwnershipDomain" xlink:label="loc_us-gaap_OwnershipDomain_7A871FE7E765C5605A52121B9411A23E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_OwnershipAxis_BC89AD353898DE1FE2A6121B94110BD8" xlink:to="loc_us-gaap_OwnershipDomain_7A871FE7E765C5605A52121B9411A23E" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_JointVenturesThatProvideElectricalTransmissionInfrastructureServicesMember" xlink:label="loc_mtz_JointVenturesThatProvideElectricalTransmissionInfrastructureServicesMember_332F2EFDFF31A534F0D3121B9412FA83" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OwnershipDomain_7A871FE7E765C5605A52121B9411A23E" xlink:to="loc_mtz_JointVenturesThatProvideElectricalTransmissionInfrastructureServicesMember_332F2EFDFF31A534F0D3121B9412FA83" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RangeAxis" xlink:label="loc_us-gaap_RangeAxis_0012EC86E765F9FC7783121B94123701" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_OtherCommitmentsTable_6516888D8A101B3F324D121B9411CAB4" xlink:to="loc_us-gaap_RangeAxis_0012EC86E765F9FC7783121B94123701" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RangeMember" xlink:label="loc_us-gaap_RangeMember_AC25D1B21FA6C263926B121B9412A093_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RangeAxis_0012EC86E765F9FC7783121B94123701" xlink:to="loc_us-gaap_RangeMember_AC25D1B21FA6C263926B121B9412A093_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RangeMember" xlink:label="loc_us-gaap_RangeMember_AC25D1B21FA6C263926B121B9412A093" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RangeAxis_0012EC86E765F9FC7783121B94123701" xlink:to="loc_us-gaap_RangeMember_AC25D1B21FA6C263926B121B9412A093" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_MinimumMember" xlink:label="loc_us-gaap_MinimumMember_D481C9365B7E9738F703121B94123F8E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RangeMember_AC25D1B21FA6C263926B121B9412A093" xlink:to="loc_us-gaap_MinimumMember_D481C9365B7E9738F703121B94123F8E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_MaximumMember" xlink:label="loc_us-gaap_MaximumMember_2FD9989EA3C8F15A0912121B9412B9A7" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RangeMember_AC25D1B21FA6C263926B121B9412A093" xlink:to="loc_us-gaap_MaximumMember_2FD9989EA3C8F15A0912121B9412B9A7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessAcquisitionAxis" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_D18C7F395DA947B95931121B94121CDE" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_OtherCommitmentsTable_6516888D8A101B3F324D121B9411CAB4" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_D18C7F395DA947B95931121B94121CDE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_59410F3436322476004E121B9412FAAA_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_D18C7F395DA947B95931121B94121CDE" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_59410F3436322476004E121B9412FAAA_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_59410F3436322476004E121B9412FAAA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_D18C7F395DA947B95931121B94121CDE" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_59410F3436322476004E121B9412FAAA" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_PacerMember" xlink:label="loc_mtz_PacerMember_FB680895C1BA8E312FE1121B941213B2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_59410F3436322476004E121B9412FAAA" xlink:to="loc_mtz_PacerMember_FB680895C1BA8E312FE1121B941213B2" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_ProportionatelyConsolidatedJointVentureOwnershipPercentage" xlink:label="loc_mtz_ProportionatelyConsolidatedJointVentureOwnershipPercentage_AF80181C0901A1079AA4121B9413A244" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherCommitmentsLineItems_CF0D148DC22E854A3342121B941241B7" xlink:to="loc_mtz_ProportionatelyConsolidatedJointVentureOwnershipPercentage_AF80181C0901A1079AA4121B9413A244" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_7107F44D76E253F567A3121B9413FDA4" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherCommitmentsLineItems_CF0D148DC22E854A3342121B941241B7" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_7107F44D76E253F567A3121B9413FDA4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DueFromJointVenturesCurrent" xlink:label="loc_us-gaap_DueFromJointVenturesCurrent_1731625201F7221A4354121D39F2F8B8" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherCommitmentsLineItems_CF0D148DC22E854A3342121B941241B7" xlink:to="loc_us-gaap_DueFromJointVenturesCurrent_1731625201F7221A4354121D39F2F8B8" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.mastec.com/role/CommitmentsAndContingenciesOtherCommitmentsAndContingenciesNarrativeDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LossContingenciesLineItems" xlink:label="loc_us-gaap_LossContingenciesLineItems_AABAEBF7B5A83E2E559FFD3D19CEB011" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LossContingenciesTable" xlink:label="loc_us-gaap_LossContingenciesTable_1AF4DEBA0A308E19E396FD3D19CB367D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LossContingenciesLineItems_AABAEBF7B5A83E2E559FFD3D19CEB011" xlink:to="loc_us-gaap_LossContingenciesTable_1AF4DEBA0A308E19E396FD3D19CB367D" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LongtermDebtTypeAxis" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_4932E1CEEDAC81B4151AFD3D19CC9D06" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_1AF4DEBA0A308E19E396FD3D19CB367D" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_4932E1CEEDAC81B4151AFD3D19CC9D06" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_F26EF2D9F59A9BBCA809FD3D19CC6516_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_4932E1CEEDAC81B4151AFD3D19CC9D06" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_F26EF2D9F59A9BBCA809FD3D19CC6516_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_F26EF2D9F59A9BBCA809FD3D19CC6516" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_4932E1CEEDAC81B4151AFD3D19CC9D06" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_F26EF2D9F59A9BBCA809FD3D19CC6516" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DomesticLineOfCreditMember" xlink:label="loc_us-gaap_DomesticLineOfCreditMember_1C743C5B0A1E8C8AEA6DFD3D19CC965C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_F26EF2D9F59A9BBCA809FD3D19CC6516" xlink:to="loc_us-gaap_DomesticLineOfCreditMember_1C743C5B0A1E8C8AEA6DFD3D19CC965C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_GuaranteeObligationsByNatureAxis" xlink:label="loc_us-gaap_GuaranteeObligationsByNatureAxis_A2E0F1384A78E9E4ED5CFD3D19CC08A3" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_1AF4DEBA0A308E19E396FD3D19CB367D" xlink:to="loc_us-gaap_GuaranteeObligationsByNatureAxis_A2E0F1384A78E9E4ED5CFD3D19CC08A3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_GuaranteeObligationsNatureDomain" xlink:label="loc_us-gaap_GuaranteeObligationsNatureDomain_8B0BF48345CF9A0995D8FD3D19CC140E_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_GuaranteeObligationsByNatureAxis_A2E0F1384A78E9E4ED5CFD3D19CC08A3" xlink:to="loc_us-gaap_GuaranteeObligationsNatureDomain_8B0BF48345CF9A0995D8FD3D19CC140E_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_GuaranteeObligationsNatureDomain" xlink:label="loc_us-gaap_GuaranteeObligationsNatureDomain_8B0BF48345CF9A0995D8FD3D19CC140E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_GuaranteeObligationsByNatureAxis_A2E0F1384A78E9E4ED5CFD3D19CC08A3" xlink:to="loc_us-gaap_GuaranteeObligationsNatureDomain_8B0BF48345CF9A0995D8FD3D19CC140E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PerformanceGuaranteeMember" xlink:label="loc_us-gaap_PerformanceGuaranteeMember_0B86FAC123268F8CCF52FD3D19CC0080" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GuaranteeObligationsNatureDomain_8B0BF48345CF9A0995D8FD3D19CC140E" xlink:to="loc_us-gaap_PerformanceGuaranteeMember_0B86FAC123268F8CCF52FD3D19CC0080" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FinancialStandbyLetterOfCreditMember" xlink:label="loc_us-gaap_FinancialStandbyLetterOfCreditMember_9E9CF3D3D917600855B0FD3D19CC4386" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GuaranteeObligationsNatureDomain_8B0BF48345CF9A0995D8FD3D19CC140E" xlink:to="loc_us-gaap_FinancialStandbyLetterOfCreditMember_9E9CF3D3D917600855B0FD3D19CC4386" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SuretyBondMember" xlink:label="loc_us-gaap_SuretyBondMember_1197AEAAC037A2BFC8D8FD3D19CCC1B6" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GuaranteeObligationsNatureDomain_8B0BF48345CF9A0995D8FD3D19CC140E" xlink:to="loc_us-gaap_SuretyBondMember_1197AEAAC037A2BFC8D8FD3D19CCC1B6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConsolidatedEntitiesAxis" xlink:label="loc_us-gaap_ConsolidatedEntitiesAxis_4AE9D291FCB06AC5C61EFD3D19CCCCDB" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_1AF4DEBA0A308E19E396FD3D19CB367D" xlink:to="loc_us-gaap_ConsolidatedEntitiesAxis_4AE9D291FCB06AC5C61EFD3D19CCCCDB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConsolidatedEntitiesDomain" xlink:label="loc_us-gaap_ConsolidatedEntitiesDomain_734FE198E9B9B96D5720FD3D19CC62AB_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConsolidatedEntitiesAxis_4AE9D291FCB06AC5C61EFD3D19CCCCDB" xlink:to="loc_us-gaap_ConsolidatedEntitiesDomain_734FE198E9B9B96D5720FD3D19CC62AB_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConsolidatedEntitiesDomain" xlink:label="loc_us-gaap_ConsolidatedEntitiesDomain_734FE198E9B9B96D5720FD3D19CC62AB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConsolidatedEntitiesAxis_4AE9D291FCB06AC5C61EFD3D19CCCCDB" xlink:to="loc_us-gaap_ConsolidatedEntitiesDomain_734FE198E9B9B96D5720FD3D19CC62AB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SubsidiariesMember" xlink:label="loc_us-gaap_SubsidiariesMember_25ABF2D0C2C10CFDE0B9FD3D19CCDEBB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConsolidatedEntitiesDomain_734FE198E9B9B96D5720FD3D19CC62AB" xlink:to="loc_us-gaap_SubsidiariesMember_25ABF2D0C2C10CFDE0B9FD3D19CCDEBB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_StatementScenarioAxis" xlink:label="loc_us-gaap_StatementScenarioAxis_008CA26FEB6E71AAC48EFD3D19CD3861" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_1AF4DEBA0A308E19E396FD3D19CB367D" xlink:to="loc_us-gaap_StatementScenarioAxis_008CA26FEB6E71AAC48EFD3D19CD3861" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScenarioUnspecifiedDomain" xlink:label="loc_us-gaap_ScenarioUnspecifiedDomain_D9F7306235A0CD33B559FD3D19CDA2E3_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementScenarioAxis_008CA26FEB6E71AAC48EFD3D19CD3861" xlink:to="loc_us-gaap_ScenarioUnspecifiedDomain_D9F7306235A0CD33B559FD3D19CDA2E3_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScenarioUnspecifiedDomain" xlink:label="loc_us-gaap_ScenarioUnspecifiedDomain_D9F7306235A0CD33B559FD3D19CDA2E3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementScenarioAxis_008CA26FEB6E71AAC48EFD3D19CD3861" xlink:to="loc_us-gaap_ScenarioUnspecifiedDomain_D9F7306235A0CD33B559FD3D19CDA2E3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScenarioPlanMember" xlink:label="loc_us-gaap_ScenarioPlanMember_48D626DAE52C252D1E1CFD3D19CD60A1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScenarioUnspecifiedDomain_D9F7306235A0CD33B559FD3D19CDA2E3" xlink:to="loc_us-gaap_ScenarioPlanMember_48D626DAE52C252D1E1CFD3D19CD60A1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LossContingenciesByNatureOfContingencyAxis" xlink:label="loc_us-gaap_LossContingenciesByNatureOfContingencyAxis_61E0B3CF206DC73E6C67FD3D19CD0110" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_1AF4DEBA0A308E19E396FD3D19CB367D" xlink:to="loc_us-gaap_LossContingenciesByNatureOfContingencyAxis_61E0B3CF206DC73E6C67FD3D19CD0110" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LossContingencyNatureDomain" xlink:label="loc_us-gaap_LossContingencyNatureDomain_9EBA803F8C470A8E55E0FD3D19CDCA68_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LossContingenciesByNatureOfContingencyAxis_61E0B3CF206DC73E6C67FD3D19CD0110" xlink:to="loc_us-gaap_LossContingencyNatureDomain_9EBA803F8C470A8E55E0FD3D19CDCA68_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LossContingencyNatureDomain" xlink:label="loc_us-gaap_LossContingencyNatureDomain_9EBA803F8C470A8E55E0FD3D19CDCA68" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LossContingenciesByNatureOfContingencyAxis_61E0B3CF206DC73E6C67FD3D19CD0110" xlink:to="loc_us-gaap_LossContingencyNatureDomain_9EBA803F8C470A8E55E0FD3D19CDCA68" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_UninsuredRiskMember" xlink:label="loc_us-gaap_UninsuredRiskMember_5969EE0472BD7EAD846CFD3D19CD964E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingencyNatureDomain_9EBA803F8C470A8E55E0FD3D19CDCA68" xlink:to="loc_us-gaap_UninsuredRiskMember_5969EE0472BD7EAD846CFD3D19CD964E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ProductOrServiceAxis" xlink:label="loc_us-gaap_ProductOrServiceAxis_C8C4027BECBBEB323E8DFD3D19CD31BC" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_1AF4DEBA0A308E19E396FD3D19CB367D" xlink:to="loc_us-gaap_ProductOrServiceAxis_C8C4027BECBBEB323E8DFD3D19CD31BC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ProductsAndServicesDomain" xlink:label="loc_us-gaap_ProductsAndServicesDomain_5DA00FA39724203F8AECFD3D19CD6A3A_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ProductOrServiceAxis_C8C4027BECBBEB323E8DFD3D19CD31BC" xlink:to="loc_us-gaap_ProductsAndServicesDomain_5DA00FA39724203F8AECFD3D19CD6A3A_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ProductsAndServicesDomain" xlink:label="loc_us-gaap_ProductsAndServicesDomain_5DA00FA39724203F8AECFD3D19CD6A3A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ProductOrServiceAxis_C8C4027BECBBEB323E8DFD3D19CD31BC" xlink:to="loc_us-gaap_ProductsAndServicesDomain_5DA00FA39724203F8AECFD3D19CD6A3A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PropertyLiabilityAndCasualtyInsuranceSegmentMember" xlink:label="loc_us-gaap_PropertyLiabilityAndCasualtyInsuranceSegmentMember_8F47961ACA2B9F53BF89FD3D19CD56C5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ProductsAndServicesDomain_5DA00FA39724203F8AECFD3D19CD6A3A" xlink:to="loc_us-gaap_PropertyLiabilityAndCasualtyInsuranceSegmentMember_8F47961ACA2B9F53BF89FD3D19CD56C5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_GroupPoliciesMember" xlink:label="loc_us-gaap_GroupPoliciesMember_F943AD8BD7907A716C5DFD3D19CDB412" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ProductsAndServicesDomain_5DA00FA39724203F8AECFD3D19CD6A3A" xlink:to="loc_us-gaap_GroupPoliciesMember_F943AD8BD7907A716C5DFD3D19CDB412" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AccidentAndHealthInsuranceSegmentMember" xlink:label="loc_us-gaap_AccidentAndHealthInsuranceSegmentMember_3045418E64905027994FFD3D19CDFE9A" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ProductsAndServicesDomain_5DA00FA39724203F8AECFD3D19CD6A3A" xlink:to="loc_us-gaap_AccidentAndHealthInsuranceSegmentMember_3045418E64905027994FFD3D19CDFE9A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BalanceSheetLocationAxis" xlink:label="loc_us-gaap_BalanceSheetLocationAxis_4A4B8A1EC232D1F198B3FD3D19CD4948" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_1AF4DEBA0A308E19E396FD3D19CB367D" xlink:to="loc_us-gaap_BalanceSheetLocationAxis_4A4B8A1EC232D1F198B3FD3D19CD4948" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BalanceSheetLocationDomain" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_9D43867C25BE0AFB92C2FD3D19CEDA3D_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_4A4B8A1EC232D1F198B3FD3D19CD4948" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_9D43867C25BE0AFB92C2FD3D19CEDA3D_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BalanceSheetLocationDomain" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_9D43867C25BE0AFB92C2FD3D19CEDA3D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_4A4B8A1EC232D1F198B3FD3D19CD4948" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_9D43867C25BE0AFB92C2FD3D19CEDA3D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_OtherNoncurrentLiabilitiesMember" xlink:label="loc_us-gaap_OtherNoncurrentLiabilitiesMember_EB9D75C4F0570DC5CEDFFD3D19CEE8FE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_9D43867C25BE0AFB92C2FD3D19CEDA3D" xlink:to="loc_us-gaap_OtherNoncurrentLiabilitiesMember_EB9D75C4F0570DC5CEDFFD3D19CEE8FE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_OtherNoncurrentAssetsMember" xlink:label="loc_us-gaap_OtherNoncurrentAssetsMember_F01E24BED63A71FC8E85FD3D19CE06F2" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_9D43867C25BE0AFB92C2FD3D19CEDA3D" xlink:to="loc_us-gaap_OtherNoncurrentAssetsMember_F01E24BED63A71FC8E85FD3D19CE06F2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CollateralAxis" xlink:label="loc_us-gaap_CollateralAxis_BB61E27A3AB4D46167B3FD3D19CE5F67" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_1AF4DEBA0A308E19E396FD3D19CB367D" xlink:to="loc_us-gaap_CollateralAxis_BB61E27A3AB4D46167B3FD3D19CE5F67" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CollateralDomain" xlink:label="loc_us-gaap_CollateralDomain_9ED9F79D0706D5391F43FD3D19CEC14E_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CollateralAxis_BB61E27A3AB4D46167B3FD3D19CE5F67" xlink:to="loc_us-gaap_CollateralDomain_9ED9F79D0706D5391F43FD3D19CEC14E_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CollateralDomain" xlink:label="loc_us-gaap_CollateralDomain_9ED9F79D0706D5391F43FD3D19CEC14E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CollateralAxis_BB61E27A3AB4D46167B3FD3D19CE5F67" xlink:to="loc_us-gaap_CollateralDomain_9ED9F79D0706D5391F43FD3D19CEC14E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CashMember" xlink:label="loc_us-gaap_CashMember_FBCFD380ED4F5ACEF4E6FD3D19CEC8A0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollateralDomain_9ED9F79D0706D5391F43FD3D19CEC14E" xlink:to="loc_us-gaap_CashMember_FBCFD380ED4F5ACEF4E6FD3D19CEC8A0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LettersOfCreditOutstandingAmount" xlink:label="loc_us-gaap_LettersOfCreditOutstandingAmount_618086B3D02E340EFB26FD3D19CED83B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_AABAEBF7B5A83E2E559FFD3D19CEB011" xlink:to="loc_us-gaap_LettersOfCreditOutstandingAmount_618086B3D02E340EFB26FD3D19CED83B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_GuaranteeObligationsMaximumExposure" xlink:label="loc_us-gaap_GuaranteeObligationsMaximumExposure_8C68146624FF0C140EC9FD3D19CED500" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_AABAEBF7B5A83E2E559FFD3D19CEB011" xlink:to="loc_us-gaap_GuaranteeObligationsMaximumExposure_8C68146624FF0C140EC9FD3D19CED500" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ContractRevenueCost" xlink:label="loc_us-gaap_ContractRevenueCost_5C1CA8B6BA7FE448C051FD3D19CEAAD5" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_AABAEBF7B5A83E2E559FFD3D19CEB011" xlink:to="loc_us-gaap_ContractRevenueCost_5C1CA8B6BA7FE448C051FD3D19CEAAD5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SelfInsuranceReserve" xlink:label="loc_us-gaap_SelfInsuranceReserve_B3A3736D9A0C08697B5CFD3D19CE1D02" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_AABAEBF7B5A83E2E559FFD3D19CEB011" xlink:to="loc_us-gaap_SelfInsuranceReserve_B3A3736D9A0C08697B5CFD3D19CE1D02" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SelfInsuranceReserveNoncurrent" xlink:label="loc_us-gaap_SelfInsuranceReserveNoncurrent_914E70D0F8BD88762CBBFD3D19CEE668" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_AABAEBF7B5A83E2E559FFD3D19CEB011" xlink:to="loc_us-gaap_SelfInsuranceReserveNoncurrent_914E70D0F8BD88762CBBFD3D19CEE668" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PledgedAssetsSeparatelyReportedOtherAssetsPledgedAsCollateralAtFairValue" xlink:label="loc_us-gaap_PledgedAssetsSeparatelyReportedOtherAssetsPledgedAsCollateralAtFairValue_2D3D146F90FEE03E92FCFD3D19CEF387" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_AABAEBF7B5A83E2E559FFD3D19CEB011" xlink:to="loc_us-gaap_PledgedAssetsSeparatelyReportedOtherAssetsPledgedAsCollateralAtFairValue_2D3D146F90FEE03E92FCFD3D19CEF387" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.mastec.com/role/CommitmentsAndContingenciesOtherGuaranteesNarrativeDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_GuaranteeObligationsLineItems" xlink:label="loc_us-gaap_GuaranteeObligationsLineItems_B7ABE89ED1F063E70652FD6D8CD52A7B" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfGuaranteeObligationsTable" xlink:label="loc_us-gaap_ScheduleOfGuaranteeObligationsTable_9196E51AA41D4F866818FD6D8CCB59C4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_GuaranteeObligationsLineItems_B7ABE89ED1F063E70652FD6D8CD52A7B" xlink:to="loc_us-gaap_ScheduleOfGuaranteeObligationsTable_9196E51AA41D4F866818FD6D8CCB59C4" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConsolidatedEntitiesAxis" xlink:label="loc_us-gaap_ConsolidatedEntitiesAxis_D29C13D97FAFC5F537E9FD4AF64EBCE0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfGuaranteeObligationsTable_9196E51AA41D4F866818FD6D8CCB59C4" xlink:to="loc_us-gaap_ConsolidatedEntitiesAxis_D29C13D97FAFC5F537E9FD4AF64EBCE0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConsolidatedEntitiesDomain" xlink:label="loc_us-gaap_ConsolidatedEntitiesDomain_BA772378AEFB31269D9DFD4AF64EB99B_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConsolidatedEntitiesAxis_D29C13D97FAFC5F537E9FD4AF64EBCE0" xlink:to="loc_us-gaap_ConsolidatedEntitiesDomain_BA772378AEFB31269D9DFD4AF64EB99B_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConsolidatedEntitiesDomain" xlink:label="loc_us-gaap_ConsolidatedEntitiesDomain_BA772378AEFB31269D9DFD4AF64EB99B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConsolidatedEntitiesAxis_D29C13D97FAFC5F537E9FD4AF64EBCE0" xlink:to="loc_us-gaap_ConsolidatedEntitiesDomain_BA772378AEFB31269D9DFD4AF64EB99B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SubsidiariesMember" xlink:label="loc_us-gaap_SubsidiariesMember_B380DB2633610260B4BCFD4AF64E6DD6" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConsolidatedEntitiesDomain_BA772378AEFB31269D9DFD4AF64EB99B" xlink:to="loc_us-gaap_SubsidiariesMember_B380DB2633610260B4BCFD4AF64E6DD6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LossContingenciesByNatureOfContingencyAxis" xlink:label="loc_us-gaap_LossContingenciesByNatureOfContingencyAxis_6395D67B4BC218739BD2FD4AF64E7EF0" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfGuaranteeObligationsTable_9196E51AA41D4F866818FD6D8CCB59C4" xlink:to="loc_us-gaap_LossContingenciesByNatureOfContingencyAxis_6395D67B4BC218739BD2FD4AF64E7EF0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LossContingencyNatureDomain" xlink:label="loc_us-gaap_LossContingencyNatureDomain_391E5B07E7BF37EADF46FD4AF64E063E_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LossContingenciesByNatureOfContingencyAxis_6395D67B4BC218739BD2FD4AF64E7EF0" xlink:to="loc_us-gaap_LossContingencyNatureDomain_391E5B07E7BF37EADF46FD4AF64E063E_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LossContingencyNatureDomain" xlink:label="loc_us-gaap_LossContingencyNatureDomain_391E5B07E7BF37EADF46FD4AF64E063E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LossContingenciesByNatureOfContingencyAxis_6395D67B4BC218739BD2FD4AF64E7EF0" xlink:to="loc_us-gaap_LossContingencyNatureDomain_391E5B07E7BF37EADF46FD4AF64E063E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_WarrantyObligationsMember" xlink:label="loc_us-gaap_WarrantyObligationsMember_C629840AC90A1D0B301FFD4AF64FB2DD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingencyNatureDomain_391E5B07E7BF37EADF46FD4AF64E063E" xlink:to="loc_us-gaap_WarrantyObligationsMember_C629840AC90A1D0B301FFD4AF64FB2DD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RangeAxis" xlink:label="loc_us-gaap_RangeAxis_D6C0AFA65EF96665115FFD4AF64FE827" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfGuaranteeObligationsTable_9196E51AA41D4F866818FD6D8CCB59C4" xlink:to="loc_us-gaap_RangeAxis_D6C0AFA65EF96665115FFD4AF64FE827" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RangeMember" xlink:label="loc_us-gaap_RangeMember_20E3CBE0872A878C0DAEFD4AF64F5DAD_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RangeAxis_D6C0AFA65EF96665115FFD4AF64FE827" xlink:to="loc_us-gaap_RangeMember_20E3CBE0872A878C0DAEFD4AF64F5DAD_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RangeMember" xlink:label="loc_us-gaap_RangeMember_20E3CBE0872A878C0DAEFD4AF64F5DAD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RangeAxis_D6C0AFA65EF96665115FFD4AF64FE827" xlink:to="loc_us-gaap_RangeMember_20E3CBE0872A878C0DAEFD4AF64F5DAD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_MinimumMember" xlink:label="loc_us-gaap_MinimumMember_D260371B0FC95C5FA09FFD4AF64F29F5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RangeMember_20E3CBE0872A878C0DAEFD4AF64F5DAD" xlink:to="loc_us-gaap_MinimumMember_D260371B0FC95C5FA09FFD4AF64F29F5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_MaximumMember" xlink:label="loc_us-gaap_MaximumMember_790F10F58E49D4CB1EDFFD4AF64FE297" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RangeMember_20E3CBE0872A878C0DAEFD4AF64F5DAD" xlink:to="loc_us-gaap_MaximumMember_790F10F58E49D4CB1EDFFD4AF64FE297" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_GuaranteeObligationsOriginAndPurpose" xlink:label="loc_us-gaap_GuaranteeObligationsOriginAndPurpose_F9DB09C8319A3D0F090CFD6D8CD5C8E4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GuaranteeObligationsLineItems_B7ABE89ED1F063E70652FD6D8CD52A7B" xlink:to="loc_us-gaap_GuaranteeObligationsOriginAndPurpose_F9DB09C8319A3D0F090CFD6D8CD5C8E4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_StandardProductWarrantyDescription" xlink:label="loc_us-gaap_StandardProductWarrantyDescription_C82E9F59E87A1ACE3ACBFD6D8CD51C96" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GuaranteeObligationsLineItems_B7ABE89ED1F063E70652FD6D8CD52A7B" xlink:to="loc_us-gaap_StandardProductWarrantyDescription_C82E9F59E87A1ACE3ACBFD6D8CD51C96" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueAssumptionsExpectedTerm" xlink:label="loc_us-gaap_FairValueAssumptionsExpectedTerm_02692755D49B99E255B2FD6D8CD5014A" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GuaranteeObligationsLineItems_B7ABE89ED1F063E70652FD6D8CD52A7B" xlink:to="loc_us-gaap_FairValueAssumptionsExpectedTerm_02692755D49B99E255B2FD6D8CD5014A" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.mastec.com/role/CondensedUnauditedConsolidatedBalanceSheets" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.mastec.com/role/CondensedUnauditedConsolidatedBalanceSheetsParenthetical" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_StatementLineItems" xlink:label="loc_us-gaap_StatementLineItems_AD114058D0E8B33296D6AA9B67F58289" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_StatementTable" xlink:label="loc_us-gaap_StatementTable_4185FDBE7851E3C3091AAA9B67F49AD8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_AD114058D0E8B33296D6AA9B67F58289" xlink:to="loc_us-gaap_StatementTable_4185FDBE7851E3C3091AAA9B67F49AD8" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AwardTypeAxis" xlink:label="loc_us-gaap_AwardTypeAxis_7B0C47137FA38D82A170AA9B67F49604" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_4185FDBE7851E3C3091AAA9B67F49AD8" xlink:to="loc_us-gaap_AwardTypeAxis_7B0C47137FA38D82A170AA9B67F49604" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_1EEE0DAB5FA60445D80EAA9B67F4A61D_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_7B0C47137FA38D82A170AA9B67F49604" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_1EEE0DAB5FA60445D80EAA9B67F4A61D_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_1EEE0DAB5FA60445D80EAA9B67F4A61D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_7B0C47137FA38D82A170AA9B67F49604" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_1EEE0DAB5FA60445D80EAA9B67F4A61D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RestrictedStockMember" xlink:label="loc_us-gaap_RestrictedStockMember_15A170C497BDECDDFEADAA9B67F4F9BA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_1EEE0DAB5FA60445D80EAA9B67F4A61D" xlink:to="loc_us-gaap_RestrictedStockMember_15A170C497BDECDDFEADAA9B67F4F9BA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_StatementEquityComponentsAxis" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_6CDB94C678DDD60CF2AAAA9B67F5AD2A" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_4185FDBE7851E3C3091AAA9B67F49AD8" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_6CDB94C678DDD60CF2AAAA9B67F5AD2A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaap_EquityComponentDomain_6F3C8BB099D87FE5C10EAA9B67F5BB34_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_6CDB94C678DDD60CF2AAAA9B67F5AD2A" xlink:to="loc_us-gaap_EquityComponentDomain_6F3C8BB099D87FE5C10EAA9B67F5BB34_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaap_EquityComponentDomain_6F3C8BB099D87FE5C10EAA9B67F5BB34" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_6CDB94C678DDD60CF2AAAA9B67F5AD2A" xlink:to="loc_us-gaap_EquityComponentDomain_6F3C8BB099D87FE5C10EAA9B67F5BB34" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CommonStockMember" xlink:label="loc_us-gaap_CommonStockMember_B680742BFB91BA2DA839AA9B67F51EDC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_6F3C8BB099D87FE5C10EAA9B67F5BB34" xlink:to="loc_us-gaap_CommonStockMember_B680742BFB91BA2DA839AA9B67F51EDC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PreferredStockParOrStatedValuePerShare" xlink:label="loc_us-gaap_PreferredStockParOrStatedValuePerShare_54C653D0AB19F0ED9BEEAA9B67F55D56" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_AD114058D0E8B33296D6AA9B67F58289" xlink:to="loc_us-gaap_PreferredStockParOrStatedValuePerShare_54C653D0AB19F0ED9BEEAA9B67F55D56" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PreferredStockSharesAuthorized" xlink:label="loc_us-gaap_PreferredStockSharesAuthorized_E1F140AE492E8B75620FAA9B67F5AB42" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_AD114058D0E8B33296D6AA9B67F58289" xlink:to="loc_us-gaap_PreferredStockSharesAuthorized_E1F140AE492E8B75620FAA9B67F5AB42" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PreferredStockSharesIssued" xlink:label="loc_us-gaap_PreferredStockSharesIssued_3A4EBAE0C568813B2DA0AA9B67F5B70D" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_AD114058D0E8B33296D6AA9B67F58289" xlink:to="loc_us-gaap_PreferredStockSharesIssued_3A4EBAE0C568813B2DA0AA9B67F5B70D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PreferredStockSharesOutstanding" xlink:label="loc_us-gaap_PreferredStockSharesOutstanding_EF728E258C438325C9C7AA9B67F544DB" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_AD114058D0E8B33296D6AA9B67F58289" xlink:to="loc_us-gaap_PreferredStockSharesOutstanding_EF728E258C438325C9C7AA9B67F544DB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CommonStockParOrStatedValuePerShare" xlink:label="loc_us-gaap_CommonStockParOrStatedValuePerShare_26B557368A297D2D2A07AA9B67F517DD" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_AD114058D0E8B33296D6AA9B67F58289" xlink:to="loc_us-gaap_CommonStockParOrStatedValuePerShare_26B557368A297D2D2A07AA9B67F517DD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CommonStockSharesAuthorized" xlink:label="loc_us-gaap_CommonStockSharesAuthorized_A2F3CDE912851A27D20DAA9B67F59155" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_AD114058D0E8B33296D6AA9B67F58289" xlink:to="loc_us-gaap_CommonStockSharesAuthorized_A2F3CDE912851A27D20DAA9B67F59155" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CommonStockSharesIssued" xlink:label="loc_us-gaap_CommonStockSharesIssued_DADA8F346B11D9F4C316AA9B67F5A122" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_AD114058D0E8B33296D6AA9B67F58289" xlink:to="loc_us-gaap_CommonStockSharesIssued_DADA8F346B11D9F4C316AA9B67F5A122" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_F1352E0FF3EC4F1744B6AA9B67F5551F" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_AD114058D0E8B33296D6AA9B67F58289" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_F1352E0FF3EC4F1744B6AA9B67F5551F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_TreasuryStockCommonShares" xlink:label="loc_us-gaap_TreasuryStockCommonShares_B2F05B3147584B144122AA9B67F62FD6" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_AD114058D0E8B33296D6AA9B67F58289" xlink:to="loc_us-gaap_TreasuryStockCommonShares_B2F05B3147584B144122AA9B67F62FD6" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.mastec.com/role/CondensedUnauditedConsolidatedStatementsOfCashFlows" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_StatementLineItems" xlink:label="loc_us-gaap_StatementLineItems_EDA1A25FDAB7D850BB2E0F2F9F0DE618" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_StatementTable" xlink:label="loc_us-gaap_StatementTable_9D9F9967BF0193D3E5D80F2F9F0CDC55" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_EDA1A25FDAB7D850BB2E0F2F9F0DE618" xlink:to="loc_us-gaap_StatementTable_9D9F9967BF0193D3E5D80F2F9F0CDC55" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ContingentConsiderationByTypeAxis" xlink:label="loc_us-gaap_ContingentConsiderationByTypeAxis_BA5E6939CBE17CB2C0150F2F9F0D3F5A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_9D9F9967BF0193D3E5D80F2F9F0CDC55" xlink:to="loc_us-gaap_ContingentConsiderationByTypeAxis_BA5E6939CBE17CB2C0150F2F9F0D3F5A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ContingentConsiderationTypeDomain" xlink:label="loc_us-gaap_ContingentConsiderationTypeDomain_CBFE0D122B94AC51DB790F2F9F0DBFEE_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ContingentConsiderationByTypeAxis_BA5E6939CBE17CB2C0150F2F9F0D3F5A" xlink:to="loc_us-gaap_ContingentConsiderationTypeDomain_CBFE0D122B94AC51DB790F2F9F0DBFEE_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ContingentConsiderationTypeDomain" xlink:label="loc_us-gaap_ContingentConsiderationTypeDomain_CBFE0D122B94AC51DB790F2F9F0DBFEE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ContingentConsiderationByTypeAxis_BA5E6939CBE17CB2C0150F2F9F0D3F5A" xlink:to="loc_us-gaap_ContingentConsiderationTypeDomain_CBFE0D122B94AC51DB790F2F9F0DBFEE" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_EarnoutArrangementsMember" xlink:label="loc_mtz_EarnoutArrangementsMember_D0495CE0EA5E5FEC030A0F2F9F0DC31C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ContingentConsiderationTypeDomain_CBFE0D122B94AC51DB790F2F9F0DBFEE" xlink:to="loc_mtz_EarnoutArrangementsMember_D0495CE0EA5E5FEC030A0F2F9F0DC31C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_4094777138DD8ACCD2760F2F9F0DE703" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_EDA1A25FDAB7D850BB2E0F2F9F0DE618" xlink:to="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_4094777138DD8ACCD2760F2F9F0DE703" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ProfitLoss" xlink:label="loc_us-gaap_ProfitLoss_02A84D27175461D846830F2F9F0DDE94" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_4094777138DD8ACCD2760F2F9F0DE703" xlink:to="loc_us-gaap_ProfitLoss_02A84D27175461D846830F2F9F0DDE94" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" xlink:label="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_CEAE65C5D92C7A9463510F2F9F0D8BAC" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_4094777138DD8ACCD2760F2F9F0DE703" xlink:to="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_CEAE65C5D92C7A9463510F2F9F0D8BAC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DepreciationDepletionAndAmortization" xlink:label="loc_us-gaap_DepreciationDepletionAndAmortization_0BB5D3FCEEAA393BCFBC0F2F9F0D66D3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_CEAE65C5D92C7A9463510F2F9F0D8BAC" xlink:to="loc_us-gaap_DepreciationDepletionAndAmortization_0BB5D3FCEEAA393BCFBC0F2F9F0D66D3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AmortizationOfFinancingCostsAndDiscounts" xlink:label="loc_us-gaap_AmortizationOfFinancingCostsAndDiscounts_F02CF40C27E4040F2EDE0F2F9F0D3A08" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_CEAE65C5D92C7A9463510F2F9F0D8BAC" xlink:to="loc_us-gaap_AmortizationOfFinancingCostsAndDiscounts_F02CF40C27E4040F2EDE0F2F9F0D3A08" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AllocatedShareBasedCompensationExpense" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_901CE58C5A18F9EFFB930F2F9F0DAEB3" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_CEAE65C5D92C7A9463510F2F9F0D8BAC" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_901CE58C5A18F9EFFB930F2F9F0DAEB3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DeferredIncomeTaxExpenseBenefit" xlink:label="loc_us-gaap_DeferredIncomeTaxExpenseBenefit_05BACD5011A224BABB670F2F9F0E92AE" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_CEAE65C5D92C7A9463510F2F9F0D8BAC" xlink:to="loc_us-gaap_DeferredIncomeTaxExpenseBenefit_05BACD5011A224BABB670F2F9F0E92AE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncomeLossFromEquityMethodInvestments" xlink:label="loc_us-gaap_IncomeLossFromEquityMethodInvestments_990734950936A60F73700F2F9F0EDB6D" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_CEAE65C5D92C7A9463510F2F9F0D8BAC" xlink:to="loc_us-gaap_IncomeLossFromEquityMethodInvestments_990734950936A60F73700F2F9F0EDB6D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_GainLossOnSalesOfAssetsAndAssetImpairmentCharges" xlink:label="loc_us-gaap_GainLossOnSalesOfAssetsAndAssetImpairmentCharges_306547A34723026AD3F70F2F9F0EA9A7" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_CEAE65C5D92C7A9463510F2F9F0D8BAC" xlink:to="loc_us-gaap_GainLossOnSalesOfAssetsAndAssetImpairmentCharges_306547A34723026AD3F70F2F9F0EA9A7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_OtherNoncashIncomeExpense" xlink:label="loc_us-gaap_OtherNoncashIncomeExpense_130BE9E26B46DFC9328E0F2F9F0E2655" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_CEAE65C5D92C7A9463510F2F9F0D8BAC" xlink:to="loc_us-gaap_OtherNoncashIncomeExpense_130BE9E26B46DFC9328E0F2F9F0E2655" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncreaseDecreaseInOperatingCapitalAbstract" xlink:label="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_979E51C08A4B4EB7C6ED0F2F9F0E66D6" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_4094777138DD8ACCD2760F2F9F0DE703" xlink:to="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_979E51C08A4B4EB7C6ED0F2F9F0E66D6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncreaseDecreaseInAccountsReceivable" xlink:label="loc_us-gaap_IncreaseDecreaseInAccountsReceivable_4BC33CCE7A03478709D80F2F9F1383A1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_979E51C08A4B4EB7C6ED0F2F9F0E66D6" xlink:to="loc_us-gaap_IncreaseDecreaseInAccountsReceivable_4BC33CCE7A03478709D80F2F9F1383A1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncreaseDecreaseInInventories" xlink:label="loc_us-gaap_IncreaseDecreaseInInventories_D970E4ACF40030CC42360F2F9F13D77C" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_979E51C08A4B4EB7C6ED0F2F9F0E66D6" xlink:to="loc_us-gaap_IncreaseDecreaseInInventories_D970E4ACF40030CC42360F2F9F13D77C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncreaseDecreaseInOtherOperatingAssets" xlink:label="loc_us-gaap_IncreaseDecreaseInOtherOperatingAssets_EBDD464EE92D3824C8CA0F2F9F138F45" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_979E51C08A4B4EB7C6ED0F2F9F0E66D6" xlink:to="loc_us-gaap_IncreaseDecreaseInOtherOperatingAssets_EBDD464EE92D3824C8CA0F2F9F138F45" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities" xlink:label="loc_us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities_B3A9CF68D28AF53110D50F2F9F135AE7" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_979E51C08A4B4EB7C6ED0F2F9F0E66D6" xlink:to="loc_us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities_B3A9CF68D28AF53110D50F2F9F135AE7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncreaseDecreaseInBillingInExcessOfCostOfEarnings" xlink:label="loc_us-gaap_IncreaseDecreaseInBillingInExcessOfCostOfEarnings_179942E364B6F19CC5CE0F2F9F14E40E" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_979E51C08A4B4EB7C6ED0F2F9F0E66D6" xlink:to="loc_us-gaap_IncreaseDecreaseInBillingInExcessOfCostOfEarnings_179942E364B6F19CC5CE0F2F9F14E40E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncreaseDecreaseInBookOverdrafts" xlink:label="loc_us-gaap_IncreaseDecreaseInBookOverdrafts_DD8A1A439CDE7A819FB90F2F9F14AAB9" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_979E51C08A4B4EB7C6ED0F2F9F0E66D6" xlink:to="loc_us-gaap_IncreaseDecreaseInBookOverdrafts_DD8A1A439CDE7A819FB90F2F9F14AAB9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncreaseDecreaseInOtherOperatingLiabilities" xlink:label="loc_us-gaap_IncreaseDecreaseInOtherOperatingLiabilities_E1AEC5DA06D3EBE95DB00F2F9F149807" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_979E51C08A4B4EB7C6ED0F2F9F0E66D6" xlink:to="loc_us-gaap_IncreaseDecreaseInOtherOperatingLiabilities_E1AEC5DA06D3EBE95DB00F2F9F149807" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_974E98E19DD5DBEF30660F2F9F14B2A1" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_4094777138DD8ACCD2760F2F9F0DE703" xlink:to="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_974E98E19DD5DBEF30660F2F9F14B2A1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_3ABC1D08122BEE81A8790F2F9F1496A0" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_EDA1A25FDAB7D850BB2E0F2F9F0DE618" xlink:to="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_3ABC1D08122BEE81A8790F2F9F1496A0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired" xlink:label="loc_us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired_8065CAFA9DD9F644500B0F2F9F14158D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_3ABC1D08122BEE81A8790F2F9F1496A0" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired_8065CAFA9DD9F644500B0F2F9F14158D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PaymentsToAcquireProductiveAssets" xlink:label="loc_us-gaap_PaymentsToAcquireProductiveAssets_1263D6EAE83D5D24A2610F2F9F141CD9" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_3ABC1D08122BEE81A8790F2F9F1496A0" xlink:to="loc_us-gaap_PaymentsToAcquireProductiveAssets_1263D6EAE83D5D24A2610F2F9F141CD9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment" xlink:label="loc_us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment_779CEE1406F898563A390F2F9F1420DC" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_3ABC1D08122BEE81A8790F2F9F1496A0" xlink:to="loc_us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment_779CEE1406F898563A390F2F9F1420DC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PaymentsToAcquireOtherInvestments" xlink:label="loc_us-gaap_PaymentsToAcquireOtherInvestments_5DEC9B466CB4E15D58D20F2F9F14EE5B" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_3ABC1D08122BEE81A8790F2F9F1496A0" xlink:to="loc_us-gaap_PaymentsToAcquireOtherInvestments_5DEC9B466CB4E15D58D20F2F9F14EE5B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ProceedsFromSaleAndMaturityOfOtherInvestments" xlink:label="loc_us-gaap_ProceedsFromSaleAndMaturityOfOtherInvestments_D28DFE33AFA39240ECDC0F2F9F14B78E" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_3ABC1D08122BEE81A8790F2F9F1496A0" xlink:to="loc_us-gaap_ProceedsFromSaleAndMaturityOfOtherInvestments_D28DFE33AFA39240ECDC0F2F9F14B78E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivities" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_345E9D625220DA2F1A710F2F9F147AD7" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_3ABC1D08122BEE81A8790F2F9F1496A0" xlink:to="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_345E9D625220DA2F1A710F2F9F147AD7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_1E33AF1ECEF0DC5F30830F2F9F1498B6" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_EDA1A25FDAB7D850BB2E0F2F9F0DE618" xlink:to="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_1E33AF1ECEF0DC5F30830F2F9F1498B6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ProceedsFromLongTermLinesOfCredit" xlink:label="loc_us-gaap_ProceedsFromLongTermLinesOfCredit_B7343B692599371037FD0F2F9F14B01F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_1E33AF1ECEF0DC5F30830F2F9F1498B6" xlink:to="loc_us-gaap_ProceedsFromLongTermLinesOfCredit_B7343B692599371037FD0F2F9F14B01F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RepaymentsOfLongTermLinesOfCredit" xlink:label="loc_us-gaap_RepaymentsOfLongTermLinesOfCredit_36123371E8FAEB88EDFE0F2F9F15D6C0" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_1E33AF1ECEF0DC5F30830F2F9F1498B6" xlink:to="loc_us-gaap_RepaymentsOfLongTermLinesOfCredit_36123371E8FAEB88EDFE0F2F9F15D6C0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RepaymentsOfOtherLongTermDebt" xlink:label="loc_us-gaap_RepaymentsOfOtherLongTermDebt_7AE02D5430DA55920E590F2F9F158F4F" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_1E33AF1ECEF0DC5F30830F2F9F1498B6" xlink:to="loc_us-gaap_RepaymentsOfOtherLongTermDebt_7AE02D5430DA55920E590F2F9F158F4F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RepaymentsOfLongTermCapitalLeaseObligations" xlink:label="loc_us-gaap_RepaymentsOfLongTermCapitalLeaseObligations_547418AA4A921544B3C70F2F9F156970" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_1E33AF1ECEF0DC5F30830F2F9F1498B6" xlink:to="loc_us-gaap_RepaymentsOfLongTermCapitalLeaseObligations_547418AA4A921544B3C70F2F9F156970" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PaymentsForRepurchaseOfCommonStock" xlink:label="loc_us-gaap_PaymentsForRepurchaseOfCommonStock_548ED5EBDDFC3BEFF2E30F2F9F152497" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_1E33AF1ECEF0DC5F30830F2F9F1498B6" xlink:to="loc_us-gaap_PaymentsForRepurchaseOfCommonStock_548ED5EBDDFC3BEFF2E30F2F9F152497" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PaymentsToMinorityShareholders" xlink:label="loc_us-gaap_PaymentsToMinorityShareholders_DA3C77E25A576FCB5FA80F2F9F1A7A29" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_1E33AF1ECEF0DC5F30830F2F9F1498B6" xlink:to="loc_us-gaap_PaymentsToMinorityShareholders_DA3C77E25A576FCB5FA80F2F9F1A7A29" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlansIncludingStockOptions" xlink:label="loc_us-gaap_ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlansIncludingStockOptions_CC1E8E8EA7501F10D2880F2F9F1AC890" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_1E33AF1ECEF0DC5F30830F2F9F1498B6" xlink:to="loc_us-gaap_ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlansIncludingStockOptions_CC1E8E8EA7501F10D2880F2F9F1AC890" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation" xlink:label="loc_us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation_CF891C8F3BAB0B944B000F2F9F1A7451" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_1E33AF1ECEF0DC5F30830F2F9F1498B6" xlink:to="loc_us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation_CF891C8F3BAB0B944B000F2F9F1A7451" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ProceedsFromPaymentsForOtherFinancingActivities" xlink:label="loc_us-gaap_ProceedsFromPaymentsForOtherFinancingActivities_CFD6C4970D184CF2795C0F2F9F1A5650" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_1E33AF1ECEF0DC5F30830F2F9F1498B6" xlink:to="loc_us-gaap_ProceedsFromPaymentsForOtherFinancingActivities_CFD6C4970D184CF2795C0F2F9F1A5650" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivities" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_D9D45CCD390FF2AC77EB0F2F9F1B5862" xlink:type="locator" />
    <link:definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_1E33AF1ECEF0DC5F30830F2F9F1498B6" xlink:to="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_D9D45CCD390FF2AC77EB0F2F9F1B5862" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EffectOfExchangeRateOnCashAndCashEquivalents" xlink:label="loc_us-gaap_EffectOfExchangeRateOnCashAndCashEquivalents_046436A82E20A168E15F0F2F9F1B9C9A" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_EDA1A25FDAB7D850BB2E0F2F9F0DE618" xlink:to="loc_us-gaap_EffectOfExchangeRateOnCashAndCashEquivalents_046436A82E20A168E15F0F2F9F1B9C9A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease" xlink:label="loc_us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease_40D374D2BD2BC21754A90F2F9F1B65E8" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_EDA1A25FDAB7D850BB2E0F2F9F0DE618" xlink:to="loc_us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease_40D374D2BD2BC21754A90F2F9F1B65E8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_2F10552E0D498015E4700F2F9F1BE807" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_EDA1A25FDAB7D850BB2E0F2F9F0DE618" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_2F10552E0D498015E4700F2F9F1BE807" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SupplementalCashFlowInformationAbstract" xlink:label="loc_us-gaap_SupplementalCashFlowInformationAbstract_B16412BEE605FC19370D0F2F9F1BF1B7" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_EDA1A25FDAB7D850BB2E0F2F9F0DE618" xlink:to="loc_us-gaap_SupplementalCashFlowInformationAbstract_B16412BEE605FC19370D0F2F9F1BF1B7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_InterestPaid" xlink:label="loc_us-gaap_InterestPaid_31654A272FE4F652015E0F2F9F1B2FD7" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SupplementalCashFlowInformationAbstract_B16412BEE605FC19370D0F2F9F1BF1B7" xlink:to="loc_us-gaap_InterestPaid_31654A272FE4F652015E0F2F9F1B2FD7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncomeTaxesPaidNet" xlink:label="loc_us-gaap_IncomeTaxesPaidNet_9016C3FA181AD8CBB9250F2F9F1B46EC" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SupplementalCashFlowInformationAbstract_B16412BEE605FC19370D0F2F9F1BF1B7" xlink:to="loc_us-gaap_IncomeTaxesPaidNet_9016C3FA181AD8CBB9250F2F9F1B46EC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract" xlink:label="loc_us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract_90CB6E55D47CADB76E4B0F2F9F1BF77B" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_EDA1A25FDAB7D850BB2E0F2F9F0DE618" xlink:to="loc_us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract_90CB6E55D47CADB76E4B0F2F9F1BF77B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessCombinationConsiderationTransferredLiabilitiesIncurred" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferredLiabilitiesIncurred_FA44CB0FE9BB8CA180F90F2F9F1BEE12" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract_90CB6E55D47CADB76E4B0F2F9F1BF77B" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferredLiabilitiesIncurred_FA44CB0FE9BB8CA180F90F2F9F1BEE12" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CapitalLeaseObligationsIncurred" xlink:label="loc_us-gaap_CapitalLeaseObligationsIncurred_FDE251C4EF30CE9D21EC0F2F9F1BE7CF" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract_90CB6E55D47CADB76E4B0F2F9F1BF77B" xlink:to="loc_us-gaap_CapitalLeaseObligationsIncurred_FDE251C4EF30CE9D21EC0F2F9F1BE7CF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CapitalExpendituresIncurredButNotYetPaid" xlink:label="loc_us-gaap_CapitalExpendituresIncurredButNotYetPaid_BBFC2C3CB1BD69DEBFDE0F2F9F1C4627" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract_90CB6E55D47CADB76E4B0F2F9F1BF77B" xlink:to="loc_us-gaap_CapitalExpendituresIncurredButNotYetPaid_BBFC2C3CB1BD69DEBFDE0F2F9F1C4627" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.mastec.com/role/CondensedUnauditedConsolidatedStatementsOfComprehensiveIncome" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.mastec.com/role/CondensedUnauditedConsolidatedStatementsOfOperations" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.mastec.com/role/Debt" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.mastec.com/role/DebtAdditionalInformationNarrativeDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentLineItems" xlink:label="loc_us-gaap_DebtInstrumentLineItems_70E8F3E3200736AFB05DD05F379871C4" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentTable" xlink:label="loc_us-gaap_DebtInstrumentTable_E55D01F648269038F04BD05F37973E33" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_70E8F3E3200736AFB05DD05F379871C4" xlink:to="loc_us-gaap_DebtInstrumentTable_E55D01F648269038F04BD05F37973E33" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BalanceSheetLocationAxis" xlink:label="loc_us-gaap_BalanceSheetLocationAxis_7EE642DAFAB6B0FC0161D05F379746C8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_E55D01F648269038F04BD05F37973E33" xlink:to="loc_us-gaap_BalanceSheetLocationAxis_7EE642DAFAB6B0FC0161D05F379746C8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BalanceSheetLocationDomain" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_8E79AAE3C33B8F03AB07D05F37972446_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_7EE642DAFAB6B0FC0161D05F379746C8" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_8E79AAE3C33B8F03AB07D05F37972446_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BalanceSheetLocationDomain" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_8E79AAE3C33B8F03AB07D05F37972446" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_7EE642DAFAB6B0FC0161D05F379746C8" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_8E79AAE3C33B8F03AB07D05F37972446" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AccruedLiabilitiesMember" xlink:label="loc_us-gaap_AccruedLiabilitiesMember_C978EB78E55E8CA490C2D05F3797F9B1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_8E79AAE3C33B8F03AB07D05F37972446" xlink:to="loc_us-gaap_AccruedLiabilitiesMember_C978EB78E55E8CA490C2D05F3797F9B1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LongtermDebtTypeAxis" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_65BB6D87A5153A594413D05F3798543F" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_E55D01F648269038F04BD05F37973E33" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_65BB6D87A5153A594413D05F3798543F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_7F367112840ACEB1F801D05F37981C6D_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_65BB6D87A5153A594413D05F3798543F" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_7F367112840ACEB1F801D05F37981C6D_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_7F367112840ACEB1F801D05F37981C6D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_65BB6D87A5153A594413D05F3798543F" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_7F367112840ACEB1F801D05F37981C6D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SeniorNotesMember" xlink:label="loc_us-gaap_SeniorNotesMember_49B8539532F5591E43A7D05F37989DE9" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_7F367112840ACEB1F801D05F37981C6D" xlink:to="loc_us-gaap_SeniorNotesMember_49B8539532F5591E43A7D05F37989DE9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentAxis" xlink:label="loc_us-gaap_DebtInstrumentAxis_7AF1D55729F927EFDC94D05F3798241D" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_E55D01F648269038F04BD05F37973E33" xlink:to="loc_us-gaap_DebtInstrumentAxis_7AF1D55729F927EFDC94D05F3798241D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_775805492415AF7A6FC8D05F3798DC40_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_7AF1D55729F927EFDC94D05F3798241D" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_775805492415AF7A6FC8D05F3798DC40_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_775805492415AF7A6FC8D05F3798DC40" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_7AF1D55729F927EFDC94D05F3798241D" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_775805492415AF7A6FC8D05F3798DC40" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_FourPointEightSevenFivePercentSeniorNotesMember" xlink:label="loc_mtz_FourPointEightSevenFivePercentSeniorNotesMember_2DCB1FE1CC9B5B6E38B6D05F3798C360" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_775805492415AF7A6FC8D05F3798DC40" xlink:to="loc_mtz_FourPointEightSevenFivePercentSeniorNotesMember_2DCB1FE1CC9B5B6E38B6D05F3798C360" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_InterestPayableCurrent" xlink:label="loc_us-gaap_InterestPayableCurrent_7BB6761CCD7E897F0692D05F379868FC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_70E8F3E3200736AFB05DD05F379871C4" xlink:to="loc_us-gaap_InterestPayableCurrent_7BB6761CCD7E897F0692D05F379868FC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_E2A3A476015171341774D05F37980329" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_70E8F3E3200736AFB05DD05F379871C4" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_E2A3A476015171341774D05F37980329" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.mastec.com/role/DebtDebtGuaranteesAndCovenantsNarrativeDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentLineItems" xlink:label="loc_us-gaap_DebtInstrumentLineItems_59B6C2A53FA55E57AAE989DC3C2E7344" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentTable" xlink:label="loc_us-gaap_DebtInstrumentTable_7BB3103B97E455C9ACF8EEB00E87B02A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_59B6C2A53FA55E57AAE989DC3C2E7344" xlink:to="loc_us-gaap_DebtInstrumentTable_7BB3103B97E455C9ACF8EEB00E87B02A" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LongtermDebtTypeAxis" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_288DB4B5F7135161952E35FE64569D35" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_7BB3103B97E455C9ACF8EEB00E87B02A" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_288DB4B5F7135161952E35FE64569D35" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_9356121C2ED48F1A6F4105C9BE56DCF0_8FF700ECD19F568F86EB052BB273C9DB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_288DB4B5F7135161952E35FE64569D35" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_9356121C2ED48F1A6F4105C9BE56DCF0_8FF700ECD19F568F86EB052BB273C9DB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_28626B70A33A5427A0B588E615993A47" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_288DB4B5F7135161952E35FE64569D35" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_28626B70A33A5427A0B588E615993A47" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SeniorNotesMember" xlink:label="loc_us-gaap_SeniorNotesMember_7AC8684D1D245253AB7B00E6181C62ED" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_28626B70A33A5427A0B588E615993A47" xlink:to="loc_us-gaap_SeniorNotesMember_7AC8684D1D245253AB7B00E6181C62ED" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentAxis" xlink:label="loc_us-gaap_DebtInstrumentAxis_7F5446C408CC526D9884ECA019B35C8E" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_7BB3103B97E455C9ACF8EEB00E87B02A" xlink:to="loc_us-gaap_DebtInstrumentAxis_7F5446C408CC526D9884ECA019B35C8E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_5BACE55D7D98BFC595B505C9BE57EE7A_8FF700ECD19F568F86EB052BB273C9DB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_7F5446C408CC526D9884ECA019B35C8E" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_5BACE55D7D98BFC595B505C9BE57EE7A_8FF700ECD19F568F86EB052BB273C9DB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_32E8BB3904A65DFEBAEE3FD60E3D97DC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_7F5446C408CC526D9884ECA019B35C8E" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_32E8BB3904A65DFEBAEE3FD60E3D97DC" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_FourPointEightSevenFivePercentSeniorNotesMember" xlink:label="loc_mtz_FourPointEightSevenFivePercentSeniorNotesMember_213DE6A260D65726923BEE73FBD8CC6F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_32E8BB3904A65DFEBAEE3FD60E3D97DC" xlink:to="loc_mtz_FourPointEightSevenFivePercentSeniorNotesMember_213DE6A260D65726923BEE73FBD8CC6F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentCollateral" xlink:label="loc_us-gaap_DebtInstrumentCollateral_E1F41BBFC3C95BE6881B83176D3EFC37" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_59B6C2A53FA55E57AAE989DC3C2E7344" xlink:to="loc_us-gaap_DebtInstrumentCollateral_E1F41BBFC3C95BE6881B83176D3EFC37" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_7F4124328A4952A2A7064CFC48274FBC" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_59B6C2A53FA55E57AAE989DC3C2E7344" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_7F4124328A4952A2A7064CFC48274FBC" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.mastec.com/role/DebtOtherCreditFacilitiesNarrativeDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentLineItems" xlink:label="loc_us-gaap_DebtInstrumentLineItems_8DC1D92143AB35B643308BCDE10902CF" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentTable" xlink:label="loc_us-gaap_DebtInstrumentTable_E704F5530B833A6D6A5B8BCDE108F4B4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_8DC1D92143AB35B643308BCDE10902CF" xlink:to="loc_us-gaap_DebtInstrumentTable_E704F5530B833A6D6A5B8BCDE108F4B4" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LongtermDebtTypeAxis" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_8ABDD2164C0F95F862348BCDE10867D0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_E704F5530B833A6D6A5B8BCDE108F4B4" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_8ABDD2164C0F95F862348BCDE10867D0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_592F7749D30F7DF0DE158BCDE108EB1C_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_8ABDD2164C0F95F862348BCDE10867D0" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_592F7749D30F7DF0DE158BCDE108EB1C_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_592F7749D30F7DF0DE158BCDE108EB1C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_8ABDD2164C0F95F862348BCDE10867D0" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_592F7749D30F7DF0DE158BCDE108EB1C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ForeignLineOfCreditMember" xlink:label="loc_us-gaap_ForeignLineOfCreditMember_E5D637DC37D69F55DF428BCDE108FD09" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_592F7749D30F7DF0DE158BCDE108EB1C" xlink:to="loc_us-gaap_ForeignLineOfCreditMember_E5D637DC37D69F55DF428BCDE108FD09" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CurrencyAxis" xlink:label="loc_us-gaap_CurrencyAxis_F934965341066C15D88C8BCDE109AAAD" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_E704F5530B833A6D6A5B8BCDE108F4B4" xlink:to="loc_us-gaap_CurrencyAxis_F934965341066C15D88C8BCDE109AAAD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.sec.gov/currency/2017/currency-2017-01-31.xsd#currency_AllCurrenciesDomain" xlink:label="loc_currency_AllCurrenciesDomain_DF4B42C27E2AE54B8ECC8BCDE10994D4_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CurrencyAxis_F934965341066C15D88C8BCDE109AAAD" xlink:to="loc_currency_AllCurrenciesDomain_DF4B42C27E2AE54B8ECC8BCDE10994D4_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.sec.gov/currency/2017/currency-2017-01-31.xsd#currency_AllCurrenciesDomain" xlink:label="loc_currency_AllCurrenciesDomain_DF4B42C27E2AE54B8ECC8BCDE10994D4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CurrencyAxis_F934965341066C15D88C8BCDE109AAAD" xlink:to="loc_currency_AllCurrenciesDomain_DF4B42C27E2AE54B8ECC8BCDE10994D4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.sec.gov/currency/2017/currency-2017-01-31.xsd#currency_CAD" xlink:label="loc_currency_CAD_DCBEA1C057F980C318C28BCDE109A5E2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_currency_AllCurrenciesDomain_DF4B42C27E2AE54B8ECC8BCDE10994D4" xlink:to="loc_currency_CAD_DCBEA1C057F980C318C28BCDE109A5E2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RangeAxis" xlink:label="loc_us-gaap_RangeAxis_087F0A9E40A698B3A68F8BCDE1091D91" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_E704F5530B833A6D6A5B8BCDE108F4B4" xlink:to="loc_us-gaap_RangeAxis_087F0A9E40A698B3A68F8BCDE1091D91" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RangeMember" xlink:label="loc_us-gaap_RangeMember_61EC9FA99A1703488B238BCDE1092569_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RangeAxis_087F0A9E40A698B3A68F8BCDE1091D91" xlink:to="loc_us-gaap_RangeMember_61EC9FA99A1703488B238BCDE1092569_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RangeMember" xlink:label="loc_us-gaap_RangeMember_61EC9FA99A1703488B238BCDE1092569" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RangeAxis_087F0A9E40A698B3A68F8BCDE1091D91" xlink:to="loc_us-gaap_RangeMember_61EC9FA99A1703488B238BCDE1092569" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_WeightedAverageMember" xlink:label="loc_us-gaap_WeightedAverageMember_8CB1B7867BAB8480B4218BCDE1092DCF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RangeMember_61EC9FA99A1703488B238BCDE1092569" xlink:to="loc_us-gaap_WeightedAverageMember_8CB1B7867BAB8480B4218BCDE1092DCF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_DDF61BF36B7152DC511A8BCDE10935E4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_8DC1D92143AB35B643308BCDE10902CF" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_DDF61BF36B7152DC511A8BCDE10935E4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentCarryingAmount" xlink:label="loc_us-gaap_DebtInstrumentCarryingAmount_386282F48855B4239AB58BCDE109365C" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_8DC1D92143AB35B643308BCDE10902CF" xlink:to="loc_us-gaap_DebtInstrumentCarryingAmount_386282F48855B4239AB58BCDE109365C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LineOfCreditFacilityInterestRateAtPeriodEnd" xlink:label="loc_us-gaap_LineOfCreditFacilityInterestRateAtPeriodEnd_D82F9618ECAC86C62C178BCDE1092B81" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_8DC1D92143AB35B643308BCDE10902CF" xlink:to="loc_us-gaap_LineOfCreditFacilityInterestRateAtPeriodEnd_D82F9618ECAC86C62C178BCDE1092B81" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LineOfCreditFacilityRationaleForClassificationAsLongTermDebt" xlink:label="loc_us-gaap_LineOfCreditFacilityRationaleForClassificationAsLongTermDebt_69CC6009709326784B0B8BCDE1097A2C" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_8DC1D92143AB35B643308BCDE10902CF" xlink:to="loc_us-gaap_LineOfCreditFacilityRationaleForClassificationAsLongTermDebt_69CC6009709326784B0B8BCDE1097A2C" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.mastec.com/role/DebtScheduleOfCarryingValuesOfDebtDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentLineItems" xlink:label="loc_us-gaap_DebtInstrumentLineItems_9E4EC2535069A5A651B0CFDEA4249C94" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentTable" xlink:label="loc_us-gaap_DebtInstrumentTable_53602737082C76F749BDCFDEA4238371" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_9E4EC2535069A5A651B0CFDEA4249C94" xlink:to="loc_us-gaap_DebtInstrumentTable_53602737082C76F749BDCFDEA4238371" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LongtermDebtTypeAxis" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_6A903C41910DBC81652ECFDEA423BCC5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_53602737082C76F749BDCFDEA4238371" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_6A903C41910DBC81652ECFDEA423BCC5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_E01862E0E8E5A77B6478CFDEA423A19B_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_6A903C41910DBC81652ECFDEA423BCC5" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_E01862E0E8E5A77B6478CFDEA423A19B_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_E01862E0E8E5A77B6478CFDEA423A19B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_6A903C41910DBC81652ECFDEA423BCC5" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_E01862E0E8E5A77B6478CFDEA423A19B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DomesticLineOfCreditMember" xlink:label="loc_us-gaap_DomesticLineOfCreditMember_DED651A21E4889E102EECFDEA4236D4D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_E01862E0E8E5A77B6478CFDEA423A19B" xlink:to="loc_us-gaap_DomesticLineOfCreditMember_DED651A21E4889E102EECFDEA4236D4D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SeniorNotesMember" xlink:label="loc_us-gaap_SeniorNotesMember_2BC640BDAF44F5912545CFDEA4237FD9" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_E01862E0E8E5A77B6478CFDEA423A19B" xlink:to="loc_us-gaap_SeniorNotesMember_2BC640BDAF44F5912545CFDEA4237FD9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CapitalLeaseObligationsMember" xlink:label="loc_us-gaap_CapitalLeaseObligationsMember_FE2EE1AA900371529A8BCFDEA423CB6C" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_E01862E0E8E5A77B6478CFDEA423A19B" xlink:to="loc_us-gaap_CapitalLeaseObligationsMember_FE2EE1AA900371529A8BCFDEA423CB6C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NotesPayableOtherPayablesMember" xlink:label="loc_us-gaap_NotesPayableOtherPayablesMember_F5454B86D66A8365A8B4CFDEA42391EF" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_E01862E0E8E5A77B6478CFDEA423A19B" xlink:to="loc_us-gaap_NotesPayableOtherPayablesMember_F5454B86D66A8365A8B4CFDEA42391EF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CreditFacilityAxis" xlink:label="loc_us-gaap_CreditFacilityAxis_7986A0A06302973E2987CFDEA423DF8D" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_53602737082C76F749BDCFDEA4238371" xlink:to="loc_us-gaap_CreditFacilityAxis_7986A0A06302973E2987CFDEA423DF8D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CreditFacilityDomain" xlink:label="loc_us-gaap_CreditFacilityDomain_6FD6FEBF7709891A9FF5CFDEA42390D4_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_7986A0A06302973E2987CFDEA423DF8D" xlink:to="loc_us-gaap_CreditFacilityDomain_6FD6FEBF7709891A9FF5CFDEA42390D4_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CreditFacilityDomain" xlink:label="loc_us-gaap_CreditFacilityDomain_6FD6FEBF7709891A9FF5CFDEA42390D4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_7986A0A06302973E2987CFDEA423DF8D" xlink:to="loc_us-gaap_CreditFacilityDomain_6FD6FEBF7709891A9FF5CFDEA42390D4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RevolvingCreditFacilityMember" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_9A885E9BA813EDB42049CFDEA423D1A9" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_6FD6FEBF7709891A9FF5CFDEA42390D4" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_9A885E9BA813EDB42049CFDEA423D1A9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LoansPayableMember" xlink:label="loc_us-gaap_LoansPayableMember_4C62ACE1C75DDC528D51CFDEA423D5C1" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_6FD6FEBF7709891A9FF5CFDEA42390D4" xlink:to="loc_us-gaap_LoansPayableMember_4C62ACE1C75DDC528D51CFDEA423D5C1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentAxis" xlink:label="loc_us-gaap_DebtInstrumentAxis_97342F56EB655F362968CFDEA4233C2E" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_53602737082C76F749BDCFDEA4238371" xlink:to="loc_us-gaap_DebtInstrumentAxis_97342F56EB655F362968CFDEA4233C2E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_F9D8D8601EECE20954F1CFDEA423F0F4_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_97342F56EB655F362968CFDEA4233C2E" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_F9D8D8601EECE20954F1CFDEA423F0F4_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_F9D8D8601EECE20954F1CFDEA423F0F4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_97342F56EB655F362968CFDEA4233C2E" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_F9D8D8601EECE20954F1CFDEA423F0F4" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_FourPointEightSevenFivePercentSeniorNotesMember" xlink:label="loc_mtz_FourPointEightSevenFivePercentSeniorNotesMember_C45BA4E1CBE885B59E2BCFDEA4243A18" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_F9D8D8601EECE20954F1CFDEA423F0F4" xlink:to="loc_mtz_FourPointEightSevenFivePercentSeniorNotesMember_C45BA4E1CBE885B59E2BCFDEA4243A18" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LineOfCreditFacilityExpirationDate1" xlink:label="loc_us-gaap_LineOfCreditFacilityExpirationDate1_7B616262C6B57BFE1214CFDEA424DE46" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_9E4EC2535069A5A651B0CFDEA4249C94" xlink:to="loc_us-gaap_LineOfCreditFacilityExpirationDate1_7B616262C6B57BFE1214CFDEA424DE46" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentCarryingAmount" xlink:label="loc_us-gaap_DebtInstrumentCarryingAmount_BD68D86602C05207079ACFDEA424C64D" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_9E4EC2535069A5A651B0CFDEA4249C94" xlink:to="loc_us-gaap_DebtInstrumentCarryingAmount_BD68D86602C05207079ACFDEA424C64D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_AC24AFBF2DC68537A14AD03167ACDED4" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_9E4EC2535069A5A651B0CFDEA4249C94" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_AC24AFBF2DC68537A14AD03167ACDED4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentMaturityDate" xlink:label="loc_us-gaap_DebtInstrumentMaturityDate_3384A26FF1A38DE38AC4CFDEA4241CDE" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_9E4EC2535069A5A651B0CFDEA4249C94" xlink:to="loc_us-gaap_DebtInstrumentMaturityDate_3384A26FF1A38DE38AC4CFDEA4241CDE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtWeightedAverageInterestRate" xlink:label="loc_us-gaap_DebtWeightedAverageInterestRate_B5826A4C195EC397760ACFDEA424B414" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_9E4EC2535069A5A651B0CFDEA4249C94" xlink:to="loc_us-gaap_DebtWeightedAverageInterestRate_B5826A4C195EC397760ACFDEA424B414" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LeaseExpirationDate1" xlink:label="loc_us-gaap_LeaseExpirationDate1_7590DF4FD51BC524B21DCFDEA42416E9" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_9E4EC2535069A5A651B0CFDEA4249C94" xlink:to="loc_us-gaap_LeaseExpirationDate1_7590DF4FD51BC524B21DCFDEA42416E9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CapitalLeaseObligations" xlink:label="loc_us-gaap_CapitalLeaseObligations_69FD734CBE0CC182DE92CFDEA4248FCF" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_9E4EC2535069A5A651B0CFDEA4249C94" xlink:to="loc_us-gaap_CapitalLeaseObligations_69FD734CBE0CC182DE92CFDEA4248FCF" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_LongtermDebtandCapitalLeaseObligationsIncludingCurrentMaturitiesGross" xlink:label="loc_mtz_LongtermDebtandCapitalLeaseObligationsIncludingCurrentMaturitiesGross_2048487DFF7E3F5414B6CFDEA424D898" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_9E4EC2535069A5A651B0CFDEA4249C94" xlink:to="loc_mtz_LongtermDebtandCapitalLeaseObligationsIncludingCurrentMaturitiesGross_2048487DFF7E3F5414B6CFDEA424D898" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DeferredFinanceCostsNet" xlink:label="loc_us-gaap_DeferredFinanceCostsNet_65EB86AACD6632117955CFDEA4241D49" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_9E4EC2535069A5A651B0CFDEA4249C94" xlink:to="loc_us-gaap_DeferredFinanceCostsNet_65EB86AACD6632117955CFDEA4241D49" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LongTermDebtAndCapitalLeaseObligationsIncludingCurrentMaturities" xlink:label="loc_us-gaap_LongTermDebtAndCapitalLeaseObligationsIncludingCurrentMaturities_C4CC28122271D9EBFB47CFDEA424075C" xlink:type="locator" />
    <link:definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_9E4EC2535069A5A651B0CFDEA4249C94" xlink:to="loc_us-gaap_LongTermDebtAndCapitalLeaseObligationsIncludingCurrentMaturities_C4CC28122271D9EBFB47CFDEA424075C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LongTermDebtAndCapitalLeaseObligationsCurrent" xlink:label="loc_us-gaap_LongTermDebtAndCapitalLeaseObligationsCurrent_1ED983244E8E2686870CCFDEA424FB5B" xlink:type="locator" />
    <link:definitionArc order="11" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_9E4EC2535069A5A651B0CFDEA4249C94" xlink:to="loc_us-gaap_LongTermDebtAndCapitalLeaseObligationsCurrent_1ED983244E8E2686870CCFDEA424FB5B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LongTermDebtAndCapitalLeaseObligations" xlink:label="loc_us-gaap_LongTermDebtAndCapitalLeaseObligations_0323AC15ABEE176ED0A2CFDEA4243217" xlink:type="locator" />
    <link:definitionArc order="12" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_9E4EC2535069A5A651B0CFDEA4249C94" xlink:to="loc_us-gaap_LongTermDebtAndCapitalLeaseObligations_0323AC15ABEE176ED0A2CFDEA4243217" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.mastec.com/role/DebtSeniorSecuredCreditFacilityNarrativeDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentLineItems" xlink:label="loc_us-gaap_DebtInstrumentLineItems_57913B22954E838BE2B4D05C8C80C42D" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentTable" xlink:label="loc_us-gaap_DebtInstrumentTable_5803DB84F5BBF01BA9B0D05C8C789188" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_57913B22954E838BE2B4D05C8C80C42D" xlink:to="loc_us-gaap_DebtInstrumentTable_5803DB84F5BBF01BA9B0D05C8C789188" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LongtermDebtTypeAxis" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_C701B01C4774C88E959FD05C8C786181" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_5803DB84F5BBF01BA9B0D05C8C789188" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_C701B01C4774C88E959FD05C8C786181" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_8E268946500CECDC344BD05C8C789D4B_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_C701B01C4774C88E959FD05C8C786181" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_8E268946500CECDC344BD05C8C789D4B_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_8E268946500CECDC344BD05C8C789D4B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_C701B01C4774C88E959FD05C8C786181" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_8E268946500CECDC344BD05C8C789D4B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DomesticLineOfCreditMember" xlink:label="loc_us-gaap_DomesticLineOfCreditMember_2CF0116743E0FD41768BD05C8C79E524" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_8E268946500CECDC344BD05C8C789D4B" xlink:to="loc_us-gaap_DomesticLineOfCreditMember_2CF0116743E0FD41768BD05C8C79E524" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CreditFacilityAxis" xlink:label="loc_us-gaap_CreditFacilityAxis_6AA2DA39E29C3C968302D05C8C79F370" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_5803DB84F5BBF01BA9B0D05C8C789188" xlink:to="loc_us-gaap_CreditFacilityAxis_6AA2DA39E29C3C968302D05C8C79F370" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CreditFacilityDomain" xlink:label="loc_us-gaap_CreditFacilityDomain_EA328963E6CA89A0138DD05C8C7908B0_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_6AA2DA39E29C3C968302D05C8C79F370" xlink:to="loc_us-gaap_CreditFacilityDomain_EA328963E6CA89A0138DD05C8C7908B0_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CreditFacilityDomain" xlink:label="loc_us-gaap_CreditFacilityDomain_EA328963E6CA89A0138DD05C8C7908B0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_6AA2DA39E29C3C968302D05C8C79F370" xlink:to="loc_us-gaap_CreditFacilityDomain_EA328963E6CA89A0138DD05C8C7908B0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RevolvingCreditFacilityMember" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_A8A366B7079D785ED4C0D05C8C79BB3B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_EA328963E6CA89A0138DD05C8C7908B0" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_A8A366B7079D785ED4C0D05C8C79BB3B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LoansPayableMember" xlink:label="loc_us-gaap_LoansPayableMember_7B850ACD83D1BE93D989D05C8C79E4DF" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_EA328963E6CA89A0138DD05C8C7908B0" xlink:to="loc_us-gaap_LoansPayableMember_7B850ACD83D1BE93D989D05C8C79E4DF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LetterOfCreditMember" xlink:label="loc_us-gaap_LetterOfCreditMember_BF34C6595ABB71ACF4EDD05C8C7998FA" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_EA328963E6CA89A0138DD05C8C7908B0" xlink:to="loc_us-gaap_LetterOfCreditMember_BF34C6595ABB71ACF4EDD05C8C7998FA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RangeAxis" xlink:label="loc_us-gaap_RangeAxis_88D91F556547C434A092D05C8C7AA3BC" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_5803DB84F5BBF01BA9B0D05C8C789188" xlink:to="loc_us-gaap_RangeAxis_88D91F556547C434A092D05C8C7AA3BC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RangeMember" xlink:label="loc_us-gaap_RangeMember_3B287BF09B393A302EFED05C8C7A87CD_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RangeAxis_88D91F556547C434A092D05C8C7AA3BC" xlink:to="loc_us-gaap_RangeMember_3B287BF09B393A302EFED05C8C7A87CD_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RangeMember" xlink:label="loc_us-gaap_RangeMember_3B287BF09B393A302EFED05C8C7A87CD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RangeAxis_88D91F556547C434A092D05C8C7AA3BC" xlink:to="loc_us-gaap_RangeMember_3B287BF09B393A302EFED05C8C7A87CD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_WeightedAverageMember" xlink:label="loc_us-gaap_WeightedAverageMember_4B3B1475B88FF4C7F44DD05C8C7A7208" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RangeMember_3B287BF09B393A302EFED05C8C7A87CD" xlink:to="loc_us-gaap_WeightedAverageMember_4B3B1475B88FF4C7F44DD05C8C7A7208" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_GuaranteeObligationsByNatureAxis" xlink:label="loc_us-gaap_GuaranteeObligationsByNatureAxis_11FEE259C7148AB118D6D05C8C7A787B" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_5803DB84F5BBF01BA9B0D05C8C789188" xlink:to="loc_us-gaap_GuaranteeObligationsByNatureAxis_11FEE259C7148AB118D6D05C8C7A787B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_GuaranteeObligationsNatureDomain" xlink:label="loc_us-gaap_GuaranteeObligationsNatureDomain_C9AF04A0576A80E949E3D05C8C7A1FE8_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_GuaranteeObligationsByNatureAxis_11FEE259C7148AB118D6D05C8C7A787B" xlink:to="loc_us-gaap_GuaranteeObligationsNatureDomain_C9AF04A0576A80E949E3D05C8C7A1FE8_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_GuaranteeObligationsNatureDomain" xlink:label="loc_us-gaap_GuaranteeObligationsNatureDomain_C9AF04A0576A80E949E3D05C8C7A1FE8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_GuaranteeObligationsByNatureAxis_11FEE259C7148AB118D6D05C8C7A787B" xlink:to="loc_us-gaap_GuaranteeObligationsNatureDomain_C9AF04A0576A80E949E3D05C8C7A1FE8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_StandbyLettersOfCreditMember" xlink:label="loc_us-gaap_StandbyLettersOfCreditMember_5615FDDA882931051D27D05C8C7A349B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GuaranteeObligationsNatureDomain_C9AF04A0576A80E949E3D05C8C7A1FE8" xlink:to="loc_us-gaap_StandbyLettersOfCreditMember_5615FDDA882931051D27D05C8C7A349B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FinancialStandbyLetterOfCreditMember" xlink:label="loc_us-gaap_FinancialStandbyLetterOfCreditMember_5684E36552E573CF584CD05C8C7A0D77" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GuaranteeObligationsNatureDomain_C9AF04A0576A80E949E3D05C8C7A1FE8" xlink:to="loc_us-gaap_FinancialStandbyLetterOfCreditMember_5684E36552E573CF584CD05C8C7A0D77" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_D7BD2C1A8B44F29F4AD7D05C8C805F82" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_57913B22954E838BE2B4D05C8C80C42D" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_D7BD2C1A8B44F29F4AD7D05C8C805F82" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LineOfCreditFacilityFrequencyOfPayments" xlink:label="loc_us-gaap_LineOfCreditFacilityFrequencyOfPayments_0067B25F4D67A89EE13FD05C8C804EC6" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_57913B22954E838BE2B4D05C8C80C42D" xlink:to="loc_us-gaap_LineOfCreditFacilityFrequencyOfPayments_0067B25F4D67A89EE13FD05C8C804EC6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LineOfCreditFacilityPeriodicPaymentPrincipal" xlink:label="loc_us-gaap_LineOfCreditFacilityPeriodicPaymentPrincipal_5066A97DB16D8CB5DC7DD05C8C801E30" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_57913B22954E838BE2B4D05C8C80C42D" xlink:to="loc_us-gaap_LineOfCreditFacilityPeriodicPaymentPrincipal_5066A97DB16D8CB5DC7DD05C8C801E30" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_LineOfCreditFacilityAmountDenominatedInForeignCurrencies" xlink:label="loc_mtz_LineOfCreditFacilityAmountDenominatedInForeignCurrencies_11EE5FFC72373FB7AA1CD05C8C80D7E2" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_57913B22954E838BE2B4D05C8C80C42D" xlink:to="loc_mtz_LineOfCreditFacilityAmountDenominatedInForeignCurrencies_11EE5FFC72373FB7AA1CD05C8C80D7E2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LineOfCreditFacilityInterestRateAtPeriodEnd" xlink:label="loc_us-gaap_LineOfCreditFacilityInterestRateAtPeriodEnd_E6526ADFAFAC2A8D611DD05C8C8026B8" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_57913B22954E838BE2B4D05C8C80C42D" xlink:to="loc_us-gaap_LineOfCreditFacilityInterestRateAtPeriodEnd_E6526ADFAFAC2A8D611DD05C8C8026B8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LettersOfCreditOutstandingAmount" xlink:label="loc_us-gaap_LettersOfCreditOutstandingAmount_27E46ACA750B2BF8ADCAD05C8C80AFB6" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_57913B22954E838BE2B4D05C8C80C42D" xlink:to="loc_us-gaap_LettersOfCreditOutstandingAmount_27E46ACA750B2BF8ADCAD05C8C80AFB6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity" xlink:label="loc_us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity_5CF434AE1A82D1002D71D05C8C8013CE" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_57913B22954E838BE2B4D05C8C80C42D" xlink:to="loc_us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity_5CF434AE1A82D1002D71D05C8C8013CE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LineOfCreditFacilityCapacityAvailableForSpecificPurposeOtherThanForTradePurchases" xlink:label="loc_us-gaap_LineOfCreditFacilityCapacityAvailableForSpecificPurposeOtherThanForTradePurchases_20A974172143995928A9D05C8C803FC4" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_57913B22954E838BE2B4D05C8C80C42D" xlink:to="loc_us-gaap_LineOfCreditFacilityCapacityAvailableForSpecificPurposeOtherThanForTradePurchases_20A974172143995928A9D05C8C803FC4" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_LineOfCreditFacilityRemainingBorrowingCapacityInForeignCurrency" xlink:label="loc_mtz_LineOfCreditFacilityRemainingBorrowingCapacityInForeignCurrency_95AF110ABCEFCFEDE1FED05C8C80D31B" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_57913B22954E838BE2B4D05C8C80C42D" xlink:to="loc_mtz_LineOfCreditFacilityRemainingBorrowingCapacityInForeignCurrency_95AF110ABCEFCFEDE1FED05C8C80D31B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage" xlink:label="loc_us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage_69315F6A359A52635C87D05C8C81B361" xlink:type="locator" />
    <link:definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_57913B22954E838BE2B4D05C8C80C42D" xlink:to="loc_us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage_69315F6A359A52635C87D05C8C81B361" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LineOfCreditFacilityCollateral" xlink:label="loc_us-gaap_LineOfCreditFacilityCollateral_9900A29A03497C704371D05C8C813D15" xlink:type="locator" />
    <link:definitionArc order="11" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_57913B22954E838BE2B4D05C8C80C42D" xlink:to="loc_us-gaap_LineOfCreditFacilityCollateral_9900A29A03497C704371D05C8C813D15" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.mastec.com/role/DebtTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.mastec.com/role/DocumentAndEntityInformation" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.mastec.com/role/EarningsPerShare" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.mastec.com/role/EarningsPerShareNarrativeDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EarningsPerShareDilutedLineItems" xlink:label="loc_us-gaap_EarningsPerShareDilutedLineItems_44C3CEC4A42CBE19F0530490CA3ACD31" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfEarningsPerShareDilutedByCommonClassTable" xlink:label="loc_us-gaap_ScheduleOfEarningsPerShareDilutedByCommonClassTable_B63D912BAE507D1C9EC40490CA394DD5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_EarningsPerShareDilutedLineItems_44C3CEC4A42CBE19F0530490CA3ACD31" xlink:to="loc_us-gaap_ScheduleOfEarningsPerShareDilutedByCommonClassTable_B63D912BAE507D1C9EC40490CA394DD5" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_StatementEquityComponentsAxis" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_8B25E0A9A8CD93EAD0940490CC00AE61" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEarningsPerShareDilutedByCommonClassTable_B63D912BAE507D1C9EC40490CA394DD5" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_8B25E0A9A8CD93EAD0940490CC00AE61" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaap_EquityComponentDomain_0D81D3D2BA5C280F80880490CCEC1BB2_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_8B25E0A9A8CD93EAD0940490CC00AE61" xlink:to="loc_us-gaap_EquityComponentDomain_0D81D3D2BA5C280F80880490CCEC1BB2_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaap_EquityComponentDomain_0D81D3D2BA5C280F80880490CCEC1BB2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_8B25E0A9A8CD93EAD0940490CC00AE61" xlink:to="loc_us-gaap_EquityComponentDomain_0D81D3D2BA5C280F80880490CCEC1BB2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_TreasuryStockCommonMember" xlink:label="loc_us-gaap_TreasuryStockCommonMember_670C6DDE2A1C714198D60490CC70F154" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_0D81D3D2BA5C280F80880490CCEC1BB2" xlink:to="loc_us-gaap_TreasuryStockCommonMember_670C6DDE2A1C714198D60490CC70F154" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareRepurchaseProgramAxis" xlink:label="loc_us-gaap_ShareRepurchaseProgramAxis_9353323F13625894D79D0490CBD47BB5" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEarningsPerShareDilutedByCommonClassTable_B63D912BAE507D1C9EC40490CA394DD5" xlink:to="loc_us-gaap_ShareRepurchaseProgramAxis_9353323F13625894D79D0490CBD47BB5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareRepurchaseProgramDomain" xlink:label="loc_us-gaap_ShareRepurchaseProgramDomain_2D76D7BBA584241CBE740490CC675017_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ShareRepurchaseProgramAxis_9353323F13625894D79D0490CBD47BB5" xlink:to="loc_us-gaap_ShareRepurchaseProgramDomain_2D76D7BBA584241CBE740490CC675017_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareRepurchaseProgramDomain" xlink:label="loc_us-gaap_ShareRepurchaseProgramDomain_2D76D7BBA584241CBE740490CC675017" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ShareRepurchaseProgramAxis_9353323F13625894D79D0490CBD47BB5" xlink:to="loc_us-gaap_ShareRepurchaseProgramDomain_2D76D7BBA584241CBE740490CC675017" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_A2016ShareRepurchaseProgramMember" xlink:label="loc_mtz_A2016ShareRepurchaseProgramMember_CA3991F07515CCA8AFFF0490CC33A52F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareRepurchaseProgramDomain_2D76D7BBA584241CBE740490CC675017" xlink:to="loc_mtz_A2016ShareRepurchaseProgramMember_CA3991F07515CCA8AFFF0490CC33A52F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EarningsPerShareReconciliationDisclosure" xlink:label="loc_us-gaap_EarningsPerShareReconciliationDisclosure_E529D68BD2E40771D387048C75237D6F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareDilutedLineItems_44C3CEC4A42CBE19F0530490CA3ACD31" xlink:to="loc_us-gaap_EarningsPerShareReconciliationDisclosure_E529D68BD2E40771D387048C75237D6F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_TreasuryStockSharesAcquired" xlink:label="loc_us-gaap_TreasuryStockSharesAcquired_9519FED81D934AA788210490CB335007" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareDilutedLineItems_44C3CEC4A42CBE19F0530490CA3ACD31" xlink:to="loc_us-gaap_TreasuryStockSharesAcquired_9519FED81D934AA788210490CB335007" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.mastec.com/role/EarningsPerShareScheduleOfEarningsPerShareInformationDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EarningsPerShareDilutedLineItems" xlink:label="loc_us-gaap_EarningsPerShareDilutedLineItems_DF9359727FAD075CF3FD121E71955EC7" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfEarningsPerShareDilutedByCommonClassTable" xlink:label="loc_us-gaap_ScheduleOfEarningsPerShareDilutedByCommonClassTable_7FC37F35CC641B2ABFFC121E71957A47" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_EarningsPerShareDilutedLineItems_DF9359727FAD075CF3FD121E71955EC7" xlink:to="loc_us-gaap_ScheduleOfEarningsPerShareDilutedByCommonClassTable_7FC37F35CC641B2ABFFC121E71957A47" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_StatementEquityComponentsAxis" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_14CE41AD49A1A4B5346A121E71957BDB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEarningsPerShareDilutedByCommonClassTable_7FC37F35CC641B2ABFFC121E71957A47" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_14CE41AD49A1A4B5346A121E71957BDB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaap_EquityComponentDomain_ED6F3D12618F60078803121E7195A6E6_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_14CE41AD49A1A4B5346A121E71957BDB" xlink:to="loc_us-gaap_EquityComponentDomain_ED6F3D12618F60078803121E7195A6E6_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaap_EquityComponentDomain_ED6F3D12618F60078803121E7195A6E6" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_14CE41AD49A1A4B5346A121E71957BDB" xlink:to="loc_us-gaap_EquityComponentDomain_ED6F3D12618F60078803121E7195A6E6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CommonStockMember" xlink:label="loc_us-gaap_CommonStockMember_BC23795A009592CACC86121E71957F62" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_ED6F3D12618F60078803121E7195A6E6" xlink:to="loc_us-gaap_CommonStockMember_BC23795A009592CACC86121E71957F62" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NetIncomeLossAttributableToParentDilutedAbstract" xlink:label="loc_us-gaap_NetIncomeLossAttributableToParentDilutedAbstract_2AA6C05E36DA7C4E1546121E719553EA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareDilutedLineItems_DF9359727FAD075CF3FD121E71955EC7" xlink:to="loc_us-gaap_NetIncomeLossAttributableToParentDilutedAbstract_2AA6C05E36DA7C4E1546121E719553EA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NetIncomeLoss" xlink:label="loc_us-gaap_NetIncomeLoss_32802F2EAF5D6B70284E121E719BBBC5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetIncomeLossAttributableToParentDilutedAbstract_2AA6C05E36DA7C4E1546121E719553EA" xlink:to="loc_us-gaap_NetIncomeLoss_32802F2EAF5D6B70284E121E719BBBC5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NetIncomeLossAttributableToParentDiluted" xlink:label="loc_us-gaap_NetIncomeLossAttributableToParentDiluted_C6B5C68B244F93836180121E719BC715" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetIncomeLossAttributableToParentDilutedAbstract_2AA6C05E36DA7C4E1546121E719553EA" xlink:to="loc_us-gaap_NetIncomeLossAttributableToParentDiluted_C6B5C68B244F93836180121E719BC715" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_E8EAA0A0044317DF0621121E719B9652" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareDilutedLineItems_DF9359727FAD075CF3FD121E71955EC7" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_E8EAA0A0044317DF0621121E719B9652" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_9B5559D82EEA8C99D3EA121E719B2E34" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_E8EAA0A0044317DF0621121E719B9652" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_9B5559D82EEA8C99D3EA121E719B2E34" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements" xlink:label="loc_us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements_28C56717EE63F44A30F4121E719B6344" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_E8EAA0A0044317DF0621121E719B9652" xlink:to="loc_us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements_28C56717EE63F44A30F4121E719B6344" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding" xlink:label="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_4B8DCBC57E99941EC13F121E719BB7D9" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_E8EAA0A0044317DF0621121E719B9652" xlink:to="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_4B8DCBC57E99941EC13F121E719BB7D9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EarningsPerShareBasicAndDilutedOtherDisclosuresAbstract" xlink:label="loc_us-gaap_EarningsPerShareBasicAndDilutedOtherDisclosuresAbstract_C0ACCC0366A2493C8899121E719BF631" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareDilutedLineItems_DF9359727FAD075CF3FD121E71955EC7" xlink:to="loc_us-gaap_EarningsPerShareBasicAndDilutedOtherDisclosuresAbstract_C0ACCC0366A2493C8899121E719BF631" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_42E6B26E011063887CA2121E719B2C47" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicAndDilutedOtherDisclosuresAbstract_C0ACCC0366A2493C8899121E719BF631" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_42E6B26E011063887CA2121E719B2C47" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.mastec.com/role/EarningsPerShareTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.mastec.com/role/Equity" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.mastec.com/role/EquityShareActivityNarrativeDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EquityClassOfTreasuryStockLineItems" xlink:label="loc_us-gaap_EquityClassOfTreasuryStockLineItems_1D7B939435CC0E97AA3D1782881C2101" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ClassOfTreasuryStockTable" xlink:label="loc_us-gaap_ClassOfTreasuryStockTable_269D2AFD61C31AE15EA917828819F645" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_EquityClassOfTreasuryStockLineItems_1D7B939435CC0E97AA3D1782881C2101" xlink:to="loc_us-gaap_ClassOfTreasuryStockTable_269D2AFD61C31AE15EA917828819F645" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareRepurchaseProgramAxis" xlink:label="loc_us-gaap_ShareRepurchaseProgramAxis_B0113E67740F7492EE7A178288198EF9" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ClassOfTreasuryStockTable_269D2AFD61C31AE15EA917828819F645" xlink:to="loc_us-gaap_ShareRepurchaseProgramAxis_B0113E67740F7492EE7A178288198EF9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareRepurchaseProgramDomain" xlink:label="loc_us-gaap_ShareRepurchaseProgramDomain_80EACF2E8B15743D2B841782881AD4EB_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ShareRepurchaseProgramAxis_B0113E67740F7492EE7A178288198EF9" xlink:to="loc_us-gaap_ShareRepurchaseProgramDomain_80EACF2E8B15743D2B841782881AD4EB_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareRepurchaseProgramDomain" xlink:label="loc_us-gaap_ShareRepurchaseProgramDomain_80EACF2E8B15743D2B841782881AD4EB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ShareRepurchaseProgramAxis_B0113E67740F7492EE7A178288198EF9" xlink:to="loc_us-gaap_ShareRepurchaseProgramDomain_80EACF2E8B15743D2B841782881AD4EB" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_A2016ShareRepurchaseProgramMember" xlink:label="loc_mtz_A2016ShareRepurchaseProgramMember_ABF88D24CBA2E7DE9EF81782881A6A30" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareRepurchaseProgramDomain_80EACF2E8B15743D2B841782881AD4EB" xlink:to="loc_mtz_A2016ShareRepurchaseProgramMember_ABF88D24CBA2E7DE9EF81782881A6A30" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_A2018ShareRepurchaseProgramMember" xlink:label="loc_mtz_A2018ShareRepurchaseProgramMember_85D7ADCAFAE75DD9437B1782881A30A7" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareRepurchaseProgramDomain_80EACF2E8B15743D2B841782881AD4EB" xlink:to="loc_mtz_A2018ShareRepurchaseProgramMember_85D7ADCAFAE75DD9437B1782881A30A7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_StatementEquityComponentsAxis" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_CD17862D24C7FD3F32B51782881AE022" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ClassOfTreasuryStockTable_269D2AFD61C31AE15EA917828819F645" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_CD17862D24C7FD3F32B51782881AE022" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaap_EquityComponentDomain_1D351C05A9ADAF21CFD91782881A25F8_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_CD17862D24C7FD3F32B51782881AE022" xlink:to="loc_us-gaap_EquityComponentDomain_1D351C05A9ADAF21CFD91782881A25F8_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaap_EquityComponentDomain_1D351C05A9ADAF21CFD91782881A25F8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_CD17862D24C7FD3F32B51782881AE022" xlink:to="loc_us-gaap_EquityComponentDomain_1D351C05A9ADAF21CFD91782881A25F8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_TreasuryStockCommonMember" xlink:label="loc_us-gaap_TreasuryStockCommonMember_16685278DB570E5C5FDC1782881B0A2C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_1D351C05A9ADAF21CFD91782881A25F8" xlink:to="loc_us-gaap_TreasuryStockCommonMember_16685278DB570E5C5FDC1782881B0A2C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SubsequentEventTypeAxis" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_BB31BB8265BFCA53CE591782881B9425" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ClassOfTreasuryStockTable_269D2AFD61C31AE15EA917828819F645" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_BB31BB8265BFCA53CE591782881B9425" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SubsequentEventTypeDomain" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_DC6CC8236A69237696DC1782881BA8CE_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_BB31BB8265BFCA53CE591782881B9425" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_DC6CC8236A69237696DC1782881BA8CE_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SubsequentEventTypeDomain" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_DC6CC8236A69237696DC1782881BA8CE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_BB31BB8265BFCA53CE591782881B9425" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_DC6CC8236A69237696DC1782881BA8CE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SubsequentEventMember" xlink:label="loc_us-gaap_SubsequentEventMember_7F29530CFC5FBC33339F1782881B20F9" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_DC6CC8236A69237696DC1782881BA8CE" xlink:to="loc_us-gaap_SubsequentEventMember_7F29530CFC5FBC33339F1782881B20F9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_TreasuryStockSharesAcquired" xlink:label="loc_us-gaap_TreasuryStockSharesAcquired_61EE29802CF541AEBA711782881C56AB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityClassOfTreasuryStockLineItems_1D7B939435CC0E97AA3D1782881C2101" xlink:to="loc_us-gaap_TreasuryStockSharesAcquired_61EE29802CF541AEBA711782881C56AB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_TreasuryStockValueAcquiredCostMethod" xlink:label="loc_us-gaap_TreasuryStockValueAcquiredCostMethod_FFF35164D7077C0908921782881C8882" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityClassOfTreasuryStockLineItems_1D7B939435CC0E97AA3D1782881C2101" xlink:to="loc_us-gaap_TreasuryStockValueAcquiredCostMethod_FFF35164D7077C0908921782881C8882" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PaymentsForRepurchaseOfCommonStock" xlink:label="loc_us-gaap_PaymentsForRepurchaseOfCommonStock_F84CF41BEAE64855853F1782881C5186" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityClassOfTreasuryStockLineItems_1D7B939435CC0E97AA3D1782881C2101" xlink:to="loc_us-gaap_PaymentsForRepurchaseOfCommonStock_F84CF41BEAE64855853F1782881C5186" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_StockRepurchaseProgramAuthorizedAmount1" xlink:label="loc_us-gaap_StockRepurchaseProgramAuthorizedAmount1_8821280937347C6B96BB1782881CD91A" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityClassOfTreasuryStockLineItems_1D7B939435CC0E97AA3D1782881C2101" xlink:to="loc_us-gaap_StockRepurchaseProgramAuthorizedAmount1_8821280937347C6B96BB1782881CD91A" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.mastec.com/role/FairValueOfFinancialInstruments" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.mastec.com/role/FairValueOfFinancialInstrumentsAssetsAndLiabilitiesMeasuredAtFairValueOnNonRecurringBasisNarrativeDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_61835D6374681C494AD214067D9D1F12" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_9AB7944F9DEC49A8482214067D9BDA41" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_61835D6374681C494AD214067D9D1F12" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_9AB7944F9DEC49A8482214067D9BDA41" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentAxis" xlink:label="loc_us-gaap_DebtInstrumentAxis_5186EC636385B89F0C1614067D9B30B2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_9AB7944F9DEC49A8482214067D9BDA41" xlink:to="loc_us-gaap_DebtInstrumentAxis_5186EC636385B89F0C1614067D9B30B2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_F37C524F73486721BCFA14067D9BCB35_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_5186EC636385B89F0C1614067D9B30B2" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_F37C524F73486721BCFA14067D9BCB35_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_F37C524F73486721BCFA14067D9BCB35" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_5186EC636385B89F0C1614067D9B30B2" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_F37C524F73486721BCFA14067D9BCB35" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_FourPointEightSevenFivePercentSeniorNotesMember" xlink:label="loc_mtz_FourPointEightSevenFivePercentSeniorNotesMember_43340F592AAADDE9C5F214067D9BA487" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_F37C524F73486721BCFA14067D9BCB35" xlink:to="loc_mtz_FourPointEightSevenFivePercentSeniorNotesMember_43340F592AAADDE9C5F214067D9BA487" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LongtermDebtTypeAxis" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_7083E934F5E5A263A0EF14067D9B0936" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_9AB7944F9DEC49A8482214067D9BDA41" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_7083E934F5E5A263A0EF14067D9B0936" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_C14F517FEA336DBB80DD14067D9B9488_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_7083E934F5E5A263A0EF14067D9B0936" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_C14F517FEA336DBB80DD14067D9B9488_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_C14F517FEA336DBB80DD14067D9B9488" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_7083E934F5E5A263A0EF14067D9B0936" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_C14F517FEA336DBB80DD14067D9B9488" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SeniorNotesMember" xlink:label="loc_us-gaap_SeniorNotesMember_CB170B0ACB0746D5304314067D9C7DE7" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_C14F517FEA336DBB80DD14067D9B9488" xlink:to="loc_us-gaap_SeniorNotesMember_CB170B0ACB0746D5304314067D9C7DE7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueByMeasurementFrequencyAxis" xlink:label="loc_us-gaap_FairValueByMeasurementFrequencyAxis_587F29F2C32AB7D5F37214067D9C561E" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_9AB7944F9DEC49A8482214067D9BDA41" xlink:to="loc_us-gaap_FairValueByMeasurementFrequencyAxis_587F29F2C32AB7D5F37214067D9C561E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueMeasurementFrequencyDomain" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_BD6287320E97E00DBAC914067D9CF932_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_587F29F2C32AB7D5F37214067D9C561E" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_BD6287320E97E00DBAC914067D9CF932_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueMeasurementFrequencyDomain" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_BD6287320E97E00DBAC914067D9CF932" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_587F29F2C32AB7D5F37214067D9C561E" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_BD6287320E97E00DBAC914067D9CF932" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueMeasurementsNonrecurringMember" xlink:label="loc_us-gaap_FairValueMeasurementsNonrecurringMember_F5E13C5FF517D2CAF85014067D9C8FE8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementFrequencyDomain_BD6287320E97E00DBAC914067D9CF932" xlink:to="loc_us-gaap_FairValueMeasurementsNonrecurringMember_F5E13C5FF517D2CAF85014067D9C8FE8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueByMeasurementBasisAxis" xlink:label="loc_us-gaap_FairValueByMeasurementBasisAxis_10DE7AE9959C0D8E7DEA14067D9C45F4" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_9AB7944F9DEC49A8482214067D9BDA41" xlink:to="loc_us-gaap_FairValueByMeasurementBasisAxis_10DE7AE9959C0D8E7DEA14067D9C45F4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember" xlink:label="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_6CC983661EA1EFC197FF14067D9C8F24_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_10DE7AE9959C0D8E7DEA14067D9C45F4" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_6CC983661EA1EFC197FF14067D9C8F24_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueDisclosureItemAmountsDomain" xlink:label="loc_us-gaap_FairValueDisclosureItemAmountsDomain_494176C3A5044D8D062D14067D9CADF2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_10DE7AE9959C0D8E7DEA14067D9C45F4" xlink:to="loc_us-gaap_FairValueDisclosureItemAmountsDomain_494176C3A5044D8D062D14067D9CADF2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember" xlink:label="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_6CC983661EA1EFC197FF14067D9C8F24" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueDisclosureItemAmountsDomain_494176C3A5044D8D062D14067D9CADF2" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_6CC983661EA1EFC197FF14067D9C8F24" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CarryingReportedAmountFairValueDisclosureMember" xlink:label="loc_us-gaap_CarryingReportedAmountFairValueDisclosureMember_716B85EE9AF0A8BB24E614067D9C026C" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueDisclosureItemAmountsDomain_494176C3A5044D8D062D14067D9CADF2" xlink:to="loc_us-gaap_CarryingReportedAmountFairValueDisclosureMember_716B85EE9AF0A8BB24E614067D9C026C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EstimateOfFairValueFairValueDisclosureMember" xlink:label="loc_us-gaap_EstimateOfFairValueFairValueDisclosureMember_03561CEF1A6E10CBCA0014067D9C66EA" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueDisclosureItemAmountsDomain_494176C3A5044D8D062D14067D9CADF2" xlink:to="loc_us-gaap_EstimateOfFairValueFairValueDisclosureMember_03561CEF1A6E10CBCA0014067D9C66EA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_C39B042EB71F65630E1E14067D9C2A2E" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_9AB7944F9DEC49A8482214067D9BDA41" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_C39B042EB71F65630E1E14067D9C2A2E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_A26AB1B7DC28A9584D1614067D9CB4E2_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_C39B042EB71F65630E1E14067D9C2A2E" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_A26AB1B7DC28A9584D1614067D9CB4E2_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_A26AB1B7DC28A9584D1614067D9CB4E2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_C39B042EB71F65630E1E14067D9C2A2E" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_A26AB1B7DC28A9584D1614067D9CB4E2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueInputsLevel1Member" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_A364B51CA35DA6AF3D0414067D9C2D57" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_A26AB1B7DC28A9584D1614067D9CB4E2" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_A364B51CA35DA6AF3D0414067D9C2D57" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_FFD5A6757C3268A431A214067D9DCE9D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_61835D6374681C494AD214067D9D1F12" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_FFD5A6757C3268A431A214067D9DCE9D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NotesPayableFairValueDisclosure" xlink:label="loc_us-gaap_NotesPayableFairValueDisclosure_78C5558E98C8FBD7063A14067D9D58A6" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_61835D6374681C494AD214067D9D1F12" xlink:to="loc_us-gaap_NotesPayableFairValueDisclosure_78C5558E98C8FBD7063A14067D9D58A6" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.mastec.com/role/FairValueOfFinancialInstrumentsAssetsAndLiabilitiesMeasuredAtFairValueOnRecurringBasisNarrativeDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_6296A247DA8FA6962744FE1D4481D788" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_149FD6168CE917E3811FFE1D447F760C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_6296A247DA8FA6962744FE1D4481D788" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_149FD6168CE917E3811FFE1D447F760C" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ContingentConsiderationByTypeAxis" xlink:label="loc_us-gaap_ContingentConsiderationByTypeAxis_3E069FBF9AD3E08C020AFE1D447FA521" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_149FD6168CE917E3811FFE1D447F760C" xlink:to="loc_us-gaap_ContingentConsiderationByTypeAxis_3E069FBF9AD3E08C020AFE1D447FA521" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ContingentConsiderationTypeDomain" xlink:label="loc_us-gaap_ContingentConsiderationTypeDomain_1C6D26A77E1E822ABA2BFE1D447FB60D_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ContingentConsiderationByTypeAxis_3E069FBF9AD3E08C020AFE1D447FA521" xlink:to="loc_us-gaap_ContingentConsiderationTypeDomain_1C6D26A77E1E822ABA2BFE1D447FB60D_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ContingentConsiderationTypeDomain" xlink:label="loc_us-gaap_ContingentConsiderationTypeDomain_1C6D26A77E1E822ABA2BFE1D447FB60D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ContingentConsiderationByTypeAxis_3E069FBF9AD3E08C020AFE1D447FA521" xlink:to="loc_us-gaap_ContingentConsiderationTypeDomain_1C6D26A77E1E822ABA2BFE1D447FB60D" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_EarnoutArrangementsMember" xlink:label="loc_mtz_EarnoutArrangementsMember_9771A4F009A636E234BCFE1D447F0BE3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ContingentConsiderationTypeDomain_1C6D26A77E1E822ABA2BFE1D447FB60D" xlink:to="loc_mtz_EarnoutArrangementsMember_9771A4F009A636E234BCFE1D447F0BE3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_6AA761282CDB79836F92FE1D447F8C73" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_149FD6168CE917E3811FFE1D447F760C" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_6AA761282CDB79836F92FE1D447F8C73" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_69A6EFAE0C848BE2340CFE1D4480782D_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_6AA761282CDB79836F92FE1D447F8C73" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_69A6EFAE0C848BE2340CFE1D4480782D_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_69A6EFAE0C848BE2340CFE1D4480782D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_6AA761282CDB79836F92FE1D447F8C73" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_69A6EFAE0C848BE2340CFE1D4480782D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueInputsLevel3Member" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_51103E1317D8133C6A86FE1D4480E633" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_69A6EFAE0C848BE2340CFE1D4480782D" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_51103E1317D8133C6A86FE1D4480E633" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueByMeasurementBasisAxis" xlink:label="loc_us-gaap_FairValueByMeasurementBasisAxis_B84B42959CB57CB6A49EFE1D4480E21E" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_149FD6168CE917E3811FFE1D447F760C" xlink:to="loc_us-gaap_FairValueByMeasurementBasisAxis_B84B42959CB57CB6A49EFE1D4480E21E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember" xlink:label="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_3B8742382169C14544B7FE1D44806C11_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_B84B42959CB57CB6A49EFE1D4480E21E" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_3B8742382169C14544B7FE1D44806C11_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueDisclosureItemAmountsDomain" xlink:label="loc_us-gaap_FairValueDisclosureItemAmountsDomain_D04883BEA7EAD95C0124FE1D4480B7D7" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_B84B42959CB57CB6A49EFE1D4480E21E" xlink:to="loc_us-gaap_FairValueDisclosureItemAmountsDomain_D04883BEA7EAD95C0124FE1D4480B7D7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember" xlink:label="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_3B8742382169C14544B7FE1D44806C11" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueDisclosureItemAmountsDomain_D04883BEA7EAD95C0124FE1D4480B7D7" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_3B8742382169C14544B7FE1D44806C11" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EstimateOfFairValueFairValueDisclosureMember" xlink:label="loc_us-gaap_EstimateOfFairValueFairValueDisclosureMember_E5705B14AA273AE12A71FE1D448045EE" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueDisclosureItemAmountsDomain_D04883BEA7EAD95C0124FE1D4480B7D7" xlink:to="loc_us-gaap_EstimateOfFairValueFairValueDisclosureMember_E5705B14AA273AE12A71FE1D448045EE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BalanceSheetLocationAxis" xlink:label="loc_us-gaap_BalanceSheetLocationAxis_F019B466E784E3B41171FE1D4480FB19" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_149FD6168CE917E3811FFE1D447F760C" xlink:to="loc_us-gaap_BalanceSheetLocationAxis_F019B466E784E3B41171FE1D4480FB19" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BalanceSheetLocationDomain" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_4B1A0ACF347F0B53C68CFE1D44803BF3_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_F019B466E784E3B41171FE1D4480FB19" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_4B1A0ACF347F0B53C68CFE1D44803BF3_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BalanceSheetLocationDomain" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_4B1A0ACF347F0B53C68CFE1D44803BF3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_F019B466E784E3B41171FE1D4480FB19" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_4B1A0ACF347F0B53C68CFE1D44803BF3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_OtherCurrentLiabilitiesMember" xlink:label="loc_us-gaap_OtherCurrentLiabilitiesMember_BFB73B3D6AF3C1832387FE1D4480A2ED" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_4B1A0ACF347F0B53C68CFE1D44803BF3" xlink:to="loc_us-gaap_OtherCurrentLiabilitiesMember_BFB73B3D6AF3C1832387FE1D4480A2ED" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_EarnoutArrangementsMember" xlink:label="loc_mtz_EarnoutArrangementsMember_792AA5C8A4A92FC9AD93FE1D4480C313" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_4B1A0ACF347F0B53C68CFE1D44803BF3" xlink:to="loc_mtz_EarnoutArrangementsMember_792AA5C8A4A92FC9AD93FE1D4480C313" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueByMeasurementFrequencyAxis" xlink:label="loc_us-gaap_FairValueByMeasurementFrequencyAxis_14184B783DA61188DCC7FE1D4480758A" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_149FD6168CE917E3811FFE1D447F760C" xlink:to="loc_us-gaap_FairValueByMeasurementFrequencyAxis_14184B783DA61188DCC7FE1D4480758A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueMeasurementFrequencyDomain" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_9DBDC20A6CD0EA3729FBFE1D44819AC8_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_14184B783DA61188DCC7FE1D4480758A" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_9DBDC20A6CD0EA3729FBFE1D44819AC8_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueMeasurementFrequencyDomain" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_9DBDC20A6CD0EA3729FBFE1D44819AC8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_14184B783DA61188DCC7FE1D4480758A" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_9DBDC20A6CD0EA3729FBFE1D44819AC8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueMeasurementsRecurringMember" xlink:label="loc_us-gaap_FairValueMeasurementsRecurringMember_622636D629F4B734BD21FE1D4481FA89" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementFrequencyDomain_9DBDC20A6CD0EA3729FBFE1D44819AC8" xlink:to="loc_us-gaap_FairValueMeasurementsRecurringMember_622636D629F4B734BD21FE1D4481FA89" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisObligations" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisObligations_CD105FC9481AEF1F5BC2FE1D4481BF7C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_6296A247DA8FA6962744FE1D4481D788" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisObligations_CD105FC9481AEF1F5BC2FE1D4481BF7C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueMeasurementsValuationTechniques" xlink:label="loc_us-gaap_FairValueMeasurementsValuationTechniques_068CBBDE161C0BD84138FE1D44812E9C" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_6296A247DA8FA6962744FE1D4481D788" xlink:to="loc_us-gaap_FairValueMeasurementsValuationTechniques_068CBBDE161C0BD84138FE1D44812E9C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueMeasurementsSignificantAssumptions" xlink:label="loc_us-gaap_FairValueMeasurementsSignificantAssumptions_336C4654D2C51CC85CBBFE1D448185FD" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_6296A247DA8FA6962744FE1D4481D788" xlink:to="loc_us-gaap_FairValueMeasurementsSignificantAssumptions_336C4654D2C51CC85CBBFE1D448185FD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessCombinationContingentConsiderationArrangementsRangeOfOutcomesValueLow" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationArrangementsRangeOfOutcomesValueLow_E1493ADCD35640A65ECBFE1D4481D66C" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_6296A247DA8FA6962744FE1D4481D788" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationArrangementsRangeOfOutcomesValueLow_E1493ADCD35640A65ECBFE1D4481D66C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessCombinationContingentConsiderationArrangementsRangeOfOutcomesValueHigh" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationArrangementsRangeOfOutcomesValueHigh_E9D276A9C83E4D10E2FEFE1D4481E1E1" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_6296A247DA8FA6962744FE1D4481D788" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationArrangementsRangeOfOutcomesValueHigh_E9D276A9C83E4D10E2FEFE1D4481E1E1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessCombinationContingentConsiderationArrangementsRangeOfOutcomesMaximumUnlimited" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationArrangementsRangeOfOutcomesMaximumUnlimited_F1BAECF1F245AA262C02FE1D44814306" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_6296A247DA8FA6962744FE1D4481D788" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationArrangementsRangeOfOutcomesMaximumUnlimited_F1BAECF1F245AA262C02FE1D44814306" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityPurchases" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityPurchases_4CB06CB40D11D3E03B51FE1D448170AC" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_6296A247DA8FA6962744FE1D4481D788" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityPurchases_4CB06CB40D11D3E03B51FE1D448170AC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_GoodwillPurchaseAccountingAdjustments" xlink:label="loc_us-gaap_GoodwillPurchaseAccountingAdjustments_992498C5D5CB28FE39CBFE1D4481CE40" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_6296A247DA8FA6962744FE1D4481D788" xlink:to="loc_us-gaap_GoodwillPurchaseAccountingAdjustments_992498C5D5CB28FE39CBFE1D4481CE40" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.mastec.com/role/FairValueOfFinancialInstrumentsEquityInvestmentsNarrativeDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_F0E15D387C13715BA48516F9E1602735" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_AEA1949FA9AB1B1C978016F9E15F0FB0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_F0E15D387C13715BA48516F9E1602735" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_AEA1949FA9AB1B1C978016F9E15F0FB0" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_85E27B55E0E48205F6A216F9E15FFDBE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_AEA1949FA9AB1B1C978016F9E15F0FB0" xlink:to="loc_us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_85E27B55E0E48205F6A216F9E15FFDBE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EquityMethodInvesteeNameDomain" xlink:label="loc_us-gaap_EquityMethodInvesteeNameDomain_807F30F5590A6A74B5CE16F9E15FD9AA_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_85E27B55E0E48205F6A216F9E15FFDBE" xlink:to="loc_us-gaap_EquityMethodInvesteeNameDomain_807F30F5590A6A74B5CE16F9E15FD9AA_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EquityMethodInvesteeNameDomain" xlink:label="loc_us-gaap_EquityMethodInvesteeNameDomain_807F30F5590A6A74B5CE16F9E15FD9AA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_85E27B55E0E48205F6A216F9E15FFDBE" xlink:to="loc_us-gaap_EquityMethodInvesteeNameDomain_807F30F5590A6A74B5CE16F9E15FD9AA" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_WahaJVsMember" xlink:label="loc_mtz_WahaJVsMember_CC9C5CB42D0D8A46243016F9E15F88E6" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityMethodInvesteeNameDomain_807F30F5590A6A74B5CE16F9E15FD9AA" xlink:to="loc_mtz_WahaJVsMember_CC9C5CB42D0D8A46243016F9E15F88E6" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_CrossCountryInfrastructureMember" xlink:label="loc_mtz_CrossCountryInfrastructureMember_0EC90111877B8ABB2ED916F9E1603756" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityMethodInvesteeNameDomain_807F30F5590A6A74B5CE16F9E15FD9AA" xlink:to="loc_mtz_CrossCountryInfrastructureMember_0EC90111877B8ABB2ED916F9E1603756" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_637A03E87147A7A4DCBC16F9E16031FB" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_AEA1949FA9AB1B1C978016F9E15F0FB0" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_637A03E87147A7A4DCBC16F9E16031FB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_89EF77173F9B5A63B50F16F9E160EB69_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_637A03E87147A7A4DCBC16F9E16031FB" xlink:to="loc_us-gaap_RelatedPartyDomain_89EF77173F9B5A63B50F16F9E160EB69_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_89EF77173F9B5A63B50F16F9E160EB69" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_637A03E87147A7A4DCBC16F9E16031FB" xlink:to="loc_us-gaap_RelatedPartyDomain_89EF77173F9B5A63B50F16F9E160EB69" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EquityMethodInvesteeMember" xlink:label="loc_us-gaap_EquityMethodInvesteeMember_7345092E2DEA9970253F16F9E160695C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_89EF77173F9B5A63B50F16F9E160EB69" xlink:to="loc_us-gaap_EquityMethodInvesteeMember_7345092E2DEA9970253F16F9E160695C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ImmediateFamilyMemberOfManagementOrPrincipalOwnerMember" xlink:label="loc_us-gaap_ImmediateFamilyMemberOfManagementOrPrincipalOwnerMember_156665EA4942CE713C1116F9E1609D66" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_89EF77173F9B5A63B50F16F9E160EB69" xlink:to="loc_us-gaap_ImmediateFamilyMemberOfManagementOrPrincipalOwnerMember_156665EA4942CE713C1116F9E1609D66" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_InvesteeMember" xlink:label="loc_us-gaap_InvesteeMember_8F71A72E7A6EF1C6E25716F9E1600A15" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_89EF77173F9B5A63B50F16F9E160EB69" xlink:to="loc_us-gaap_InvesteeMember_8F71A72E7A6EF1C6E25716F9E1600A15" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EquityMethodInvestmentOwnershipPercentage" xlink:label="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_710B4307876FDC1BAFA916F9E1605A15" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_F0E15D387C13715BA48516F9E1602735" xlink:to="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_710B4307876FDC1BAFA916F9E1605A15" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_EquitySecuritiesWithoutReadilyDeterminableFairValueAmount" xlink:label="loc_mtz_EquitySecuritiesWithoutReadilyDeterminableFairValueAmount_5E961207C9DFC19C44CC16F9E160F75B" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_F0E15D387C13715BA48516F9E1602735" xlink:to="loc_mtz_EquitySecuritiesWithoutReadilyDeterminableFairValueAmount_5E961207C9DFC19C44CC16F9E160F75B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures" xlink:label="loc_us-gaap_InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures_B5C1D76F6A5F463295E316F9E160522B" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_F0E15D387C13715BA48516F9E1602735" xlink:to="loc_us-gaap_InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures_B5C1D76F6A5F463295E316F9E160522B" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.mastec.com/role/FairValueOfFinancialInstrumentsOtherInvestmentsPacerNarrativeDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_71C7FC7E72F5D68C0226121E70F1A93E" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_93801B0C0DDA04935F90121E70F0CD23" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_71C7FC7E72F5D68C0226121E70F1A93E" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_93801B0C0DDA04935F90121E70F0CD23" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessAcquisitionAxis" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_325C3EB892E6CCE98500121E70F07C29" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_93801B0C0DDA04935F90121E70F0CD23" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_325C3EB892E6CCE98500121E70F07C29" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_DF7B09EACE293C8C30AE121E70F06FE0_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_325C3EB892E6CCE98500121E70F07C29" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_DF7B09EACE293C8C30AE121E70F06FE0_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_DF7B09EACE293C8C30AE121E70F06FE0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_325C3EB892E6CCE98500121E70F07C29" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_DF7B09EACE293C8C30AE121E70F06FE0" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_PacerMember" xlink:label="loc_mtz_PacerMember_259B5D9B3C74023BA17A121E70F0B807" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_DF7B09EACE293C8C30AE121E70F06FE0" xlink:to="loc_mtz_PacerMember_259B5D9B3C74023BA17A121E70F0B807" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_39E2F8E9E0F1DDA08840121E70F01BDD" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_93801B0C0DDA04935F90121E70F0CD23" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_39E2F8E9E0F1DDA08840121E70F01BDD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_8775D82A51EEB83A96C9121E70F1324A_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_39E2F8E9E0F1DDA08840121E70F01BDD" xlink:to="loc_us-gaap_RelatedPartyDomain_8775D82A51EEB83A96C9121E70F1324A_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_8775D82A51EEB83A96C9121E70F1324A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_39E2F8E9E0F1DDA08840121E70F01BDD" xlink:to="loc_us-gaap_RelatedPartyDomain_8775D82A51EEB83A96C9121E70F1324A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_InvesteeMember" xlink:label="loc_us-gaap_InvesteeMember_500129755CD07AC5A6AE121E70F192CF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_8775D82A51EEB83A96C9121E70F1324A" xlink:to="loc_us-gaap_InvesteeMember_500129755CD07AC5A6AE121E70F192CF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CurrencyAxis" xlink:label="loc_us-gaap_CurrencyAxis_C47582E4C1CDD994E2DC121E70F1BF40" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_93801B0C0DDA04935F90121E70F0CD23" xlink:to="loc_us-gaap_CurrencyAxis_C47582E4C1CDD994E2DC121E70F1BF40" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.sec.gov/currency/2017/currency-2017-01-31.xsd#currency_AllCurrenciesDomain" xlink:label="loc_currency_AllCurrenciesDomain_60CBC2BD3E96CF18D21B121E70F169DB_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CurrencyAxis_C47582E4C1CDD994E2DC121E70F1BF40" xlink:to="loc_currency_AllCurrenciesDomain_60CBC2BD3E96CF18D21B121E70F169DB_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.sec.gov/currency/2017/currency-2017-01-31.xsd#currency_AllCurrenciesDomain" xlink:label="loc_currency_AllCurrenciesDomain_60CBC2BD3E96CF18D21B121E70F169DB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CurrencyAxis_C47582E4C1CDD994E2DC121E70F1BF40" xlink:to="loc_currency_AllCurrenciesDomain_60CBC2BD3E96CF18D21B121E70F169DB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.sec.gov/currency/2017/currency-2017-01-31.xsd#currency_CAD" xlink:label="loc_currency_CAD_A79890CCF2C1B228B1BC121E70F15C51" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_currency_AllCurrenciesDomain_60CBC2BD3E96CF18D21B121E70F169DB" xlink:to="loc_currency_CAD_A79890CCF2C1B228B1BC121E70F15C51" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ProceedsFromDivestitureOfInterestInSubsidiariesAndAffiliates" xlink:label="loc_us-gaap_ProceedsFromDivestitureOfInterestInSubsidiariesAndAffiliates_B7BC401E1B0A12190B47121E70F1B65F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_71C7FC7E72F5D68C0226121E70F1A93E" xlink:to="loc_us-gaap_ProceedsFromDivestitureOfInterestInSubsidiariesAndAffiliates_B7BC401E1B0A12190B47121E70F1B65F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures" xlink:label="loc_us-gaap_InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures_618D98CA8973718ACD4C121E70F107B4" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_71C7FC7E72F5D68C0226121E70F1A93E" xlink:to="loc_us-gaap_InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures_618D98CA8973718ACD4C121E70F107B4" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.mastec.com/role/FairValueOfFinancialInstrumentsOtherInvestmentsPensareNarrativeDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_EF88E6805C904384CA3616F9E15104A9" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_219753AC9E9B614D808516F9E14FAAC6" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_EF88E6805C904384CA3616F9E15104A9" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_219753AC9E9B614D808516F9E14FAAC6" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_BD2A9F626F73A42363C616F9E14F2508" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_219753AC9E9B614D808516F9E14FAAC6" xlink:to="loc_us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_BD2A9F626F73A42363C616F9E14F2508" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EquityMethodInvesteeNameDomain" xlink:label="loc_us-gaap_EquityMethodInvesteeNameDomain_BE60D488086D5668921616F9E150EC2E_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_BD2A9F626F73A42363C616F9E14F2508" xlink:to="loc_us-gaap_EquityMethodInvesteeNameDomain_BE60D488086D5668921616F9E150EC2E_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EquityMethodInvesteeNameDomain" xlink:label="loc_us-gaap_EquityMethodInvesteeNameDomain_BE60D488086D5668921616F9E150EC2E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_BD2A9F626F73A42363C616F9E14F2508" xlink:to="loc_us-gaap_EquityMethodInvesteeNameDomain_BE60D488086D5668921616F9E150EC2E" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_PensareMember" xlink:label="loc_mtz_PensareMember_8C45362A9F71B1BCD58616F9E1509E2A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityMethodInvesteeNameDomain_BE60D488086D5668921616F9E150EC2E" xlink:to="loc_mtz_PensareMember_8C45362A9F71B1BCD58616F9E1509E2A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_A3F42F0F2041BA50100016F9E1500964" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_219753AC9E9B614D808516F9E14FAAC6" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_A3F42F0F2041BA50100016F9E1500964" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_8BD64B56972E47B6C9CA16F9E15096D2_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_A3F42F0F2041BA50100016F9E1500964" xlink:to="loc_us-gaap_RelatedPartyDomain_8BD64B56972E47B6C9CA16F9E15096D2_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_8BD64B56972E47B6C9CA16F9E15096D2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_A3F42F0F2041BA50100016F9E1500964" xlink:to="loc_us-gaap_RelatedPartyDomain_8BD64B56972E47B6C9CA16F9E15096D2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ChiefExecutiveOfficerMember" xlink:label="loc_us-gaap_ChiefExecutiveOfficerMember_89CCDCBFC5AE70A0913716F9E150BC86" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_8BD64B56972E47B6C9CA16F9E15096D2" xlink:to="loc_us-gaap_ChiefExecutiveOfficerMember_89CCDCBFC5AE70A0913716F9E150BC86" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DerivativeInstrumentRiskAxis" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_7D4CFAB3FC2A4581E6AC16F9E1508219" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_219753AC9E9B614D808516F9E14FAAC6" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_7D4CFAB3FC2A4581E6AC16F9E1508219" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DerivativeContractTypeDomain" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_7072A2039500793F74FF16F9E1503DFA_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_7D4CFAB3FC2A4581E6AC16F9E1508219" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_7072A2039500793F74FF16F9E1503DFA_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DerivativeContractTypeDomain" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_7072A2039500793F74FF16F9E1503DFA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_7D4CFAB3FC2A4581E6AC16F9E1508219" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_7072A2039500793F74FF16F9E1503DFA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_WarrantMember" xlink:label="loc_us-gaap_WarrantMember_A7F8CCD1A7F9D132087F16F9E150A33F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_7072A2039500793F74FF16F9E1503DFA" xlink:to="loc_us-gaap_WarrantMember_A7F8CCD1A7F9D132087F16F9E150A33F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_StatementScenarioAxis" xlink:label="loc_us-gaap_StatementScenarioAxis_D8F3CE1D217EE676F8A616F9E150DB20" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_219753AC9E9B614D808516F9E14FAAC6" xlink:to="loc_us-gaap_StatementScenarioAxis_D8F3CE1D217EE676F8A616F9E150DB20" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScenarioUnspecifiedDomain" xlink:label="loc_us-gaap_ScenarioUnspecifiedDomain_F8D08BEA4A014B26F5BA16F9E151F441_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementScenarioAxis_D8F3CE1D217EE676F8A616F9E150DB20" xlink:to="loc_us-gaap_ScenarioUnspecifiedDomain_F8D08BEA4A014B26F5BA16F9E151F441_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScenarioUnspecifiedDomain" xlink:label="loc_us-gaap_ScenarioUnspecifiedDomain_F8D08BEA4A014B26F5BA16F9E151F441" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementScenarioAxis_D8F3CE1D217EE676F8A616F9E150DB20" xlink:to="loc_us-gaap_ScenarioUnspecifiedDomain_F8D08BEA4A014B26F5BA16F9E151F441" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScenarioPlanMember" xlink:label="loc_us-gaap_ScenarioPlanMember_F28F4B347B26CECE10AA16F9E1514719" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScenarioUnspecifiedDomain_F8D08BEA4A014B26F5BA16F9E151F441" xlink:to="loc_us-gaap_ScenarioPlanMember_F28F4B347B26CECE10AA16F9E1514719" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.sec.gov/invest/2013/invest-2013-01-31.xsd#invest_InvestmentAxis" xlink:label="loc_invest_InvestmentAxis_23BAA827C3A9B808ECB816F9E150BD7E" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_219753AC9E9B614D808516F9E14FAAC6" xlink:to="loc_invest_InvestmentAxis_23BAA827C3A9B808ECB816F9E150BD7E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.sec.gov/invest/2013/invest-2013-01-31.xsd#invest_InvestmentDomain" xlink:label="loc_invest_InvestmentDomain_85A9CCB2EE9A112ABF3116F9E15088F5_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_invest_InvestmentAxis_23BAA827C3A9B808ECB816F9E150BD7E" xlink:to="loc_invest_InvestmentDomain_85A9CCB2EE9A112ABF3116F9E15088F5_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.sec.gov/invest/2013/invest-2013-01-31.xsd#invest_InvestmentDomain" xlink:label="loc_invest_InvestmentDomain_85A9CCB2EE9A112ABF3116F9E15088F5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_invest_InvestmentAxis_23BAA827C3A9B808ECB816F9E150BD7E" xlink:to="loc_invest_InvestmentDomain_85A9CCB2EE9A112ABF3116F9E15088F5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CommonStockMember" xlink:label="loc_us-gaap_CommonStockMember_0F860947EACDF75809A516F9E1503D7D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_invest_InvestmentDomain_85A9CCB2EE9A112ABF3116F9E15088F5" xlink:to="loc_us-gaap_CommonStockMember_0F860947EACDF75809A516F9E1503D7D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PaymentsToAcquireLongtermInvestments" xlink:label="loc_us-gaap_PaymentsToAcquireLongtermInvestments_F47117559BA47F30545116F9E1519755" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_EF88E6805C904384CA3616F9E15104A9" xlink:to="loc_us-gaap_PaymentsToAcquireLongtermInvestments_F47117559BA47F30545116F9E1519755" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_EquityInvestmentWithoutReadilyDeterminableFairValueOwnershipPercentage" xlink:label="loc_mtz_EquityInvestmentWithoutReadilyDeterminableFairValueOwnershipPercentage_6E3FD2FB529E51077D9516F9E151F491" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_EF88E6805C904384CA3616F9E15104A9" xlink:to="loc_mtz_EquityInvestmentWithoutReadilyDeterminableFairValueOwnershipPercentage_6E3FD2FB529E51077D9516F9E151F491" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DerivativeNumberOfInstrumentsHeld" xlink:label="loc_us-gaap_DerivativeNumberOfInstrumentsHeld_EFDE3965C96B57C49CAE16F9E1515F54" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_EF88E6805C904384CA3616F9E15104A9" xlink:to="loc_us-gaap_DerivativeNumberOfInstrumentsHeld_EFDE3965C96B57C49CAE16F9E1515F54" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_InvestmentRestrictionPeriod" xlink:label="loc_mtz_InvestmentRestrictionPeriod_C18A22FF673C477CE61816F9E1516C74" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_EF88E6805C904384CA3616F9E15104A9" xlink:to="loc_mtz_InvestmentRestrictionPeriod_C18A22FF673C477CE61816F9E1516C74" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.sec.gov/invest/2013/invest-2013-01-31.xsd#invest_InvestmentWarrantsExercisePrice" xlink:label="loc_invest_InvestmentWarrantsExercisePrice_48DD289562DE5698453B16F9E151DCBD" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_EF88E6805C904384CA3616F9E15104A9" xlink:to="loc_invest_InvestmentWarrantsExercisePrice_48DD289562DE5698453B16F9E151DCBD" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.mastec.com/role/FairValueOfFinancialInstrumentsTheWahaJvsNarrativeDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_3CB76EC59B990A817FDB16F9E1593782" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_037C1507BE7F2767D60516F9E158FA81" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_3CB76EC59B990A817FDB16F9E1593782" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_037C1507BE7F2767D60516F9E158FA81" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_6C3B0CF1CFB42BA808B016F9E158CC17" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_037C1507BE7F2767D60516F9E158FA81" xlink:to="loc_us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_6C3B0CF1CFB42BA808B016F9E158CC17" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EquityMethodInvesteeNameDomain" xlink:label="loc_us-gaap_EquityMethodInvesteeNameDomain_7428256F3CE88529C01916F9E15820C9_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_6C3B0CF1CFB42BA808B016F9E158CC17" xlink:to="loc_us-gaap_EquityMethodInvesteeNameDomain_7428256F3CE88529C01916F9E15820C9_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EquityMethodInvesteeNameDomain" xlink:label="loc_us-gaap_EquityMethodInvesteeNameDomain_7428256F3CE88529C01916F9E15820C9" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_6C3B0CF1CFB42BA808B016F9E158CC17" xlink:to="loc_us-gaap_EquityMethodInvesteeNameDomain_7428256F3CE88529C01916F9E15820C9" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_WahaJVsMember" xlink:label="loc_mtz_WahaJVsMember_8A08F1F45F01F8C81DD616F9E158F5C4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityMethodInvesteeNameDomain_7428256F3CE88529C01916F9E15820C9" xlink:to="loc_mtz_WahaJVsMember_8A08F1F45F01F8C81DD616F9E158F5C4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_1B3C0CE5097A9980396A16F9E158B6D4" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_037C1507BE7F2767D60516F9E158FA81" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_1B3C0CE5097A9980396A16F9E158B6D4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_8BC6CCE538A1C0ABC24A16F9E1583ED4_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_1B3C0CE5097A9980396A16F9E158B6D4" xlink:to="loc_us-gaap_RelatedPartyDomain_8BC6CCE538A1C0ABC24A16F9E1583ED4_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_8BC6CCE538A1C0ABC24A16F9E1583ED4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_1B3C0CE5097A9980396A16F9E158B6D4" xlink:to="loc_us-gaap_RelatedPartyDomain_8BC6CCE538A1C0ABC24A16F9E1583ED4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EquityMethodInvesteeMember" xlink:label="loc_us-gaap_EquityMethodInvesteeMember_8CBF0D0098477FEF560E16F9E158469E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_8BC6CCE538A1C0ABC24A16F9E1583ED4" xlink:to="loc_us-gaap_EquityMethodInvesteeMember_8CBF0D0098477FEF560E16F9E158469E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LongtermDebtTypeAxis" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_7D0DC181F7849A381C2C16F9E158FAD5" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_037C1507BE7F2767D60516F9E158FA81" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_7D0DC181F7849A381C2C16F9E158FAD5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_AE213971730A0722E22E16F9E1591DD5_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_7D0DC181F7849A381C2C16F9E158FAD5" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_AE213971730A0722E22E16F9E1591DD5_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_AE213971730A0722E22E16F9E1591DD5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_7D0DC181F7849A381C2C16F9E158FAD5" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_AE213971730A0722E22E16F9E1591DD5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DomesticLineOfCreditMember" xlink:label="loc_us-gaap_DomesticLineOfCreditMember_9CD198F07A2671C386A616F9E159F0FB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_AE213971730A0722E22E16F9E1591DD5" xlink:to="loc_us-gaap_DomesticLineOfCreditMember_9CD198F07A2671C386A616F9E159F0FB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_GuaranteeObligationsByNatureAxis" xlink:label="loc_us-gaap_GuaranteeObligationsByNatureAxis_41B8192E2962DEE71A3916F9E1599669" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_037C1507BE7F2767D60516F9E158FA81" xlink:to="loc_us-gaap_GuaranteeObligationsByNatureAxis_41B8192E2962DEE71A3916F9E1599669" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_GuaranteeObligationsNatureDomain" xlink:label="loc_us-gaap_GuaranteeObligationsNatureDomain_5A418992C441249FE72216F9E159AFC5_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_GuaranteeObligationsByNatureAxis_41B8192E2962DEE71A3916F9E1599669" xlink:to="loc_us-gaap_GuaranteeObligationsNatureDomain_5A418992C441249FE72216F9E159AFC5_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_GuaranteeObligationsNatureDomain" xlink:label="loc_us-gaap_GuaranteeObligationsNatureDomain_5A418992C441249FE72216F9E159AFC5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_GuaranteeObligationsByNatureAxis_41B8192E2962DEE71A3916F9E1599669" xlink:to="loc_us-gaap_GuaranteeObligationsNatureDomain_5A418992C441249FE72216F9E159AFC5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FinancialStandbyLetterOfCreditMember" xlink:label="loc_us-gaap_FinancialStandbyLetterOfCreditMember_DE09FB48D8AF80024DF516F9E1597A15" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GuaranteeObligationsNatureDomain_5A418992C441249FE72216F9E159AFC5" xlink:to="loc_us-gaap_FinancialStandbyLetterOfCreditMember_DE09FB48D8AF80024DF516F9E1597A15" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_StatementBusinessSegmentsAxis" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_658F6B4EE1647132272316F9E1593949" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_037C1507BE7F2767D60516F9E158FA81" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_658F6B4EE1647132272316F9E1593949" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SegmentDomain" xlink:label="loc_us-gaap_SegmentDomain_96F60698A085CE28DC0716F9E159341E_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_658F6B4EE1647132272316F9E1593949" xlink:to="loc_us-gaap_SegmentDomain_96F60698A085CE28DC0716F9E159341E_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SegmentDomain" xlink:label="loc_us-gaap_SegmentDomain_96F60698A085CE28DC0716F9E159341E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_658F6B4EE1647132272316F9E1593949" xlink:to="loc_us-gaap_SegmentDomain_96F60698A085CE28DC0716F9E159341E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AllOtherSegmentsMember" xlink:label="loc_us-gaap_AllOtherSegmentsMember_6EC958162B1A163567FE16F9E159EAF3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_96F60698A085CE28DC0716F9E159341E" xlink:to="loc_us-gaap_AllOtherSegmentsMember_6EC958162B1A163567FE16F9E159EAF3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DerivativeInstrumentRiskAxis" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_5DB60ED58A445331DBF916F9E159886B" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_037C1507BE7F2767D60516F9E158FA81" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_5DB60ED58A445331DBF916F9E159886B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DerivativeContractTypeDomain" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_E8CF23C5C5746715484E16F9E159ECE1_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_5DB60ED58A445331DBF916F9E159886B" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_E8CF23C5C5746715484E16F9E159ECE1_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DerivativeContractTypeDomain" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_E8CF23C5C5746715484E16F9E159ECE1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_5DB60ED58A445331DBF916F9E159886B" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_E8CF23C5C5746715484E16F9E159ECE1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_InterestRateSwapMember" xlink:label="loc_us-gaap_InterestRateSwapMember_9D53D3E639D52FF8469216F9E159FFDB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_E8CF23C5C5746715484E16F9E159ECE1" xlink:to="loc_us-gaap_InterestRateSwapMember_9D53D3E639D52FF8469216F9E159FFDB" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_NumberOfPipelinesInOperation" xlink:label="loc_mtz_NumberOfPipelinesInOperation_438BA260EB87004B3A9316F9E15A9463" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_3CB76EC59B990A817FDB16F9E1593782" xlink:to="loc_mtz_NumberOfPipelinesInOperation_438BA260EB87004B3A9316F9E15A9463" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PaymentsToAcquireEquityMethodInvestments" xlink:label="loc_us-gaap_PaymentsToAcquireEquityMethodInvestments_78DFA19DB82F79D2799616F9E15A6A03" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_3CB76EC59B990A817FDB16F9E1593782" xlink:to="loc_us-gaap_PaymentsToAcquireEquityMethodInvestments_78DFA19DB82F79D2799616F9E15A6A03" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LettersOfCreditOutstandingAmount" xlink:label="loc_us-gaap_LettersOfCreditOutstandingAmount_7ECACFF450060DB3457616F9E15A2DD4" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_3CB76EC59B990A817FDB16F9E1593782" xlink:to="loc_us-gaap_LettersOfCreditOutstandingAmount_7ECACFF450060DB3457616F9E15A2DD4" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_EquityCommitmentsPercentageSatisfied" xlink:label="loc_mtz_EquityCommitmentsPercentageSatisfied_2C73B4F2B80737DBD63016F9E15A501C" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_3CB76EC59B990A817FDB16F9E1593782" xlink:to="loc_mtz_EquityCommitmentsPercentageSatisfied_2C73B4F2B80737DBD63016F9E15A501C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncomeLossFromEquityMethodInvestments" xlink:label="loc_us-gaap_IncomeLossFromEquityMethodInvestments_0C771AECC513312490D216F9E15AE136" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_3CB76EC59B990A817FDB16F9E1593782" xlink:to="loc_us-gaap_IncomeLossFromEquityMethodInvestments_0C771AECC513312490D216F9E15AE136" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RetainedEarningsUndistributedEarningsFromEquityMethodInvestees" xlink:label="loc_us-gaap_RetainedEarningsUndistributedEarningsFromEquityMethodInvestees_9F2BE6E59914E547450916F9E15A0E70" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_3CB76EC59B990A817FDB16F9E1593782" xlink:to="loc_us-gaap_RetainedEarningsUndistributedEarningsFromEquityMethodInvestees_9F2BE6E59914E547450916F9E15A0E70" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ProceedsFromEquityMethodInvestmentDividendsOrDistributionsReturnOfCapital" xlink:label="loc_us-gaap_ProceedsFromEquityMethodInvestmentDividendsOrDistributionsReturnOfCapital_A39F5CA3A34658B9BEC616F9E15A0A83" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_3CB76EC59B990A817FDB16F9E1593782" xlink:to="loc_us-gaap_ProceedsFromEquityMethodInvestmentDividendsOrDistributionsReturnOfCapital_A39F5CA3A34658B9BEC616F9E15A0A83" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures" xlink:label="loc_us-gaap_InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures_12382FAEF900743016B216F9E15AC111" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_3CB76EC59B990A817FDB16F9E1593782" xlink:to="loc_us-gaap_InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures_12382FAEF900743016B216F9E15AC111" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RevenueFromRelatedParties" xlink:label="loc_us-gaap_RevenueFromRelatedParties_9E18291390CE746050FB16F9E15AB1AA" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_3CB76EC59B990A817FDB16F9E1593782" xlink:to="loc_us-gaap_RevenueFromRelatedParties_9E18291390CE746050FB16F9E15AB1AA" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_AccountsReceivableNetOfBillingsInExcessOfCostsRelatedParties" xlink:label="loc_mtz_AccountsReceivableNetOfBillingsInExcessOfCostsRelatedParties_8BFF7C1FD84C39AAD1E916F9E15A468C" xlink:type="locator" />
    <link:definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_3CB76EC59B990A817FDB16F9E1593782" xlink:to="loc_mtz_AccountsReceivableNetOfBillingsInExcessOfCostsRelatedParties_8BFF7C1FD84C39AAD1E916F9E15A468C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodBeforeTax" xlink:label="loc_us-gaap_OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodBeforeTax_E952816234809E37670516F9E15A67C9" xlink:type="locator" />
    <link:definitionArc order="11" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_3CB76EC59B990A817FDB16F9E1593782" xlink:to="loc_us-gaap_OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodBeforeTax_E952816234809E37670516F9E15A67C9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodNetOfTax" xlink:label="loc_us-gaap_OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodNetOfTax_1EA0EA3B0924E6C7F51D16F9E15A8F01" xlink:type="locator" />
    <link:definitionArc order="12" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_3CB76EC59B990A817FDB16F9E1593782" xlink:to="loc_us-gaap_OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodNetOfTax_1EA0EA3B0924E6C7F51D16F9E15A8F01" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.mastec.com/role/GoodwillAndOtherIntangibleAssets" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.mastec.com/role/GoodwillAndOtherIntangibleAssets2017AcquisitionsNarrativeDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessAcquisitionLineItems" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_C38842A5A2FA47E8072316F9E187461C" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_BB5BEABEB0B6AE3832EA16F9E186D56A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_C38842A5A2FA47E8072316F9E187461C" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_BB5BEABEB0B6AE3832EA16F9E186D56A" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessAcquisitionAxis" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_C6CD49D9D25589B816AC16F9E186971A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_BB5BEABEB0B6AE3832EA16F9E186D56A" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_C6CD49D9D25589B816AC16F9E186971A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_E5FBB334D4E878FF08EE16F9E186FA3F_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_C6CD49D9D25589B816AC16F9E186971A" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_E5FBB334D4E878FF08EE16F9E186FA3F_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_E5FBB334D4E878FF08EE16F9E186FA3F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_C6CD49D9D25589B816AC16F9E186971A" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_E5FBB334D4E878FF08EE16F9E186FA3F" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_A2017AcquisitionsMember" xlink:label="loc_mtz_A2017AcquisitionsMember_7E1A951F6E5169EE8C7716F9E18621F7" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_E5FBB334D4E878FF08EE16F9E186FA3F" xlink:to="loc_mtz_A2017AcquisitionsMember_7E1A951F6E5169EE8C7716F9E18621F7" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_CommunicationsAcquisitionIn2017Member" xlink:label="loc_mtz_CommunicationsAcquisitionIn2017Member_D71998074B1D6F08FB9E16F9E1864F91" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_E5FBB334D4E878FF08EE16F9E186FA3F" xlink:to="loc_mtz_CommunicationsAcquisitionIn2017Member_D71998074B1D6F08FB9E16F9E1864F91" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_PowerGenerationAndIndustrialAcquisitionIn2017Member" xlink:label="loc_mtz_PowerGenerationAndIndustrialAcquisitionIn2017Member_754F7B0E3E25718AACB916F9E1861880" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_E5FBB334D4E878FF08EE16F9E186FA3F" xlink:to="loc_mtz_PowerGenerationAndIndustrialAcquisitionIn2017Member_754F7B0E3E25718AACB916F9E1861880" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_OilAndGas2017AcquisitionMember" xlink:label="loc_mtz_OilAndGas2017AcquisitionMember_A700600BAE09FC37E7AB16F9E186C327" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_E5FBB334D4E878FF08EE16F9E186FA3F" xlink:to="loc_mtz_OilAndGas2017AcquisitionMember_A700600BAE09FC37E7AB16F9E186C327" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_64A138C1BA45C8422AF316F9E187DA87" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_BB5BEABEB0B6AE3832EA16F9E186D56A" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_64A138C1BA45C8422AF316F9E187DA87" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_E1B1AEA9F23134F823CA16F9E187061A_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_64A138C1BA45C8422AF316F9E187DA87" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_E1B1AEA9F23134F823CA16F9E187061A_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_E1B1AEA9F23134F823CA16F9E187061A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_64A138C1BA45C8422AF316F9E187DA87" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_E1B1AEA9F23134F823CA16F9E187061A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CustomerRelationshipsMember" xlink:label="loc_us-gaap_CustomerRelationshipsMember_A11F52F43422BF13640B16F9E18755D9" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_E1B1AEA9F23134F823CA16F9E187061A" xlink:to="loc_us-gaap_CustomerRelationshipsMember_A11F52F43422BF13640B16F9E18755D9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_OrderOrProductionBacklogMember" xlink:label="loc_us-gaap_OrderOrProductionBacklogMember_2CE2848A2F328A54910E16F9E187A31E" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_E1B1AEA9F23134F823CA16F9E187061A" xlink:to="loc_us-gaap_OrderOrProductionBacklogMember_2CE2848A2F328A54910E16F9E187A31E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_OtherIntangibleAssetsMember" xlink:label="loc_us-gaap_OtherIntangibleAssetsMember_7CAF70E2733A55EB2C9F16F9E187FB71" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_E1B1AEA9F23134F823CA16F9E187061A" xlink:to="loc_us-gaap_OtherIntangibleAssetsMember_7CAF70E2733A55EB2C9F16F9E187FB71" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ContingentConsiderationByTypeAxis" xlink:label="loc_us-gaap_ContingentConsiderationByTypeAxis_4211DD26AC571733241516F9E187780B" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_BB5BEABEB0B6AE3832EA16F9E186D56A" xlink:to="loc_us-gaap_ContingentConsiderationByTypeAxis_4211DD26AC571733241516F9E187780B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ContingentConsiderationTypeDomain" xlink:label="loc_us-gaap_ContingentConsiderationTypeDomain_CB536779C8B89ED88F5F16F9E187DD4F_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ContingentConsiderationByTypeAxis_4211DD26AC571733241516F9E187780B" xlink:to="loc_us-gaap_ContingentConsiderationTypeDomain_CB536779C8B89ED88F5F16F9E187DD4F_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ContingentConsiderationTypeDomain" xlink:label="loc_us-gaap_ContingentConsiderationTypeDomain_CB536779C8B89ED88F5F16F9E187DD4F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ContingentConsiderationByTypeAxis_4211DD26AC571733241516F9E187780B" xlink:to="loc_us-gaap_ContingentConsiderationTypeDomain_CB536779C8B89ED88F5F16F9E187DD4F" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_EarnoutArrangementsMember" xlink:label="loc_mtz_EarnoutArrangementsMember_E30578C87620E4CA13F516F9E1873FA3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ContingentConsiderationTypeDomain_CB536779C8B89ED88F5F16F9E187DD4F" xlink:to="loc_mtz_EarnoutArrangementsMember_E30578C87620E4CA13F516F9E1873FA3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NumberOfBusinessesAcquired" xlink:label="loc_us-gaap_NumberOfBusinessesAcquired_9588FABF7517FFB8B7C816F9E187A715" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_C38842A5A2FA47E8072316F9E187461C" xlink:to="loc_us-gaap_NumberOfBusinessesAcquired_9588FABF7517FFB8B7C816F9E187A715" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired" xlink:label="loc_us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired_783CF655E508107151EC16F9E1875925" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_C38842A5A2FA47E8072316F9E187461C" xlink:to="loc_us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired_783CF655E508107151EC16F9E1875925" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessAcquisitionDescriptionOfAcquiredEntity" xlink:label="loc_us-gaap_BusinessAcquisitionDescriptionOfAcquiredEntity_7DB991007A8B53CA9C7E16F9E1875879" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_C38842A5A2FA47E8072316F9E187461C" xlink:to="loc_us-gaap_BusinessAcquisitionDescriptionOfAcquiredEntity_7DB991007A8B53CA9C7E16F9E1875879" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife" xlink:label="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife_276671D15F0679799EF516F9E18826F8" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_C38842A5A2FA47E8072316F9E187461C" xlink:to="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife_276671D15F0679799EF516F9E18826F8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessCombinationGoodwillRecognizedDescription" xlink:label="loc_us-gaap_BusinessCombinationGoodwillRecognizedDescription_C465CD85C3DCCED0C1CB16F9E1885291" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_C38842A5A2FA47E8072316F9E187461C" xlink:to="loc_us-gaap_BusinessCombinationGoodwillRecognizedDescription_C465CD85C3DCCED0C1CB16F9E1885291" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessAcquisitionPurchasePriceAllocationGoodwillExpectedTaxDeductibleAmount" xlink:label="loc_us-gaap_BusinessAcquisitionPurchasePriceAllocationGoodwillExpectedTaxDeductibleAmount_D3485C7AED58AD82205A16F9E18874E3" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_C38842A5A2FA47E8072316F9E187461C" xlink:to="loc_us-gaap_BusinessAcquisitionPurchasePriceAllocationGoodwillExpectedTaxDeductibleAmount_D3485C7AED58AD82205A16F9E18874E3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessCombinationContingentConsiderationArrangementsBasisForAmount" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationArrangementsBasisForAmount_2F961CC3B69FDF5CD51816F9E1882D67" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_C38842A5A2FA47E8072316F9E187461C" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationArrangementsBasisForAmount_2F961CC3B69FDF5CD51816F9E1882D67" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueAssumptionsExpectedTerm" xlink:label="loc_us-gaap_FairValueAssumptionsExpectedTerm_A8BFF4B69A956FA8E42E16F9E188B5E6" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_C38842A5A2FA47E8072316F9E187461C" xlink:to="loc_us-gaap_FairValueAssumptionsExpectedTerm_A8BFF4B69A956FA8E42E16F9E188B5E6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueMeasurementsValuationTechniques" xlink:label="loc_us-gaap_FairValueMeasurementsValuationTechniques_EDEFCE2421FC20FB94E416F9E188756F" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_C38842A5A2FA47E8072316F9E187461C" xlink:to="loc_us-gaap_FairValueMeasurementsValuationTechniques_EDEFCE2421FC20FB94E416F9E188756F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueMeasurementsSignificantAssumptions" xlink:label="loc_us-gaap_FairValueMeasurementsSignificantAssumptions_18C9D1F4DA05C1A5ACF816F9E188D449" xlink:type="locator" />
    <link:definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_C38842A5A2FA47E8072316F9E187461C" xlink:to="loc_us-gaap_FairValueMeasurementsSignificantAssumptions_18C9D1F4DA05C1A5ACF816F9E188D449" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessCombinationContingentConsiderationArrangementsRangeOfOutcomesValueLow" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationArrangementsRangeOfOutcomesValueLow_E6B96A0E2B9C19D4067616F9E1883584" xlink:type="locator" />
    <link:definitionArc order="11" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_C38842A5A2FA47E8072316F9E187461C" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationArrangementsRangeOfOutcomesValueLow_E6B96A0E2B9C19D4067616F9E1883584" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessCombinationContingentConsiderationArrangementsRangeOfOutcomesValueHigh" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationArrangementsRangeOfOutcomesValueHigh_114DE245532FF41D2B5D16F9E188539F" xlink:type="locator" />
    <link:definitionArc order="12" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_C38842A5A2FA47E8072316F9E187461C" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationArrangementsRangeOfOutcomesValueHigh_114DE245532FF41D2B5D16F9E188539F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessCombinationContingentConsiderationArrangementsRangeOfOutcomesMaximumUnlimited" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationArrangementsRangeOfOutcomesMaximumUnlimited_504B705FB8AD1AB75CA516F9E188671B" xlink:type="locator" />
    <link:definitionArc order="13" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_C38842A5A2FA47E8072316F9E187461C" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationArrangementsRangeOfOutcomesMaximumUnlimited_504B705FB8AD1AB75CA516F9E188671B" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.mastec.com/role/GoodwillAndOtherIntangibleAssets2018AcquisitionsNarrativeDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessAcquisitionLineItems" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_F4E9D8E68E6BB0F1326C16F9E18EE579" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_7F2D024B12858FA1917316F9E18D7851" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_F4E9D8E68E6BB0F1326C16F9E18EE579" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_7F2D024B12858FA1917316F9E18D7851" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessAcquisitionAxis" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_0EA25574DD6627445B3416F9E18E29E5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_7F2D024B12858FA1917316F9E18D7851" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_0EA25574DD6627445B3416F9E18E29E5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_4E09C0317FA02CC1550116F9E18E1126_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_0EA25574DD6627445B3416F9E18E29E5" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_4E09C0317FA02CC1550116F9E18E1126_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_4E09C0317FA02CC1550116F9E18E1126" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_0EA25574DD6627445B3416F9E18E29E5" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_4E09C0317FA02CC1550116F9E18E1126" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_A2018AcquisitionsMember" xlink:label="loc_mtz_A2018AcquisitionsMember_D665B236B9F31683C08F16F9E18EC34C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_4E09C0317FA02CC1550116F9E18E1126" xlink:to="loc_mtz_A2018AcquisitionsMember_D665B236B9F31683C08F16F9E18EC34C" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_PowerGenerationAndIndustrialAcquisitionAIn2018Member" xlink:label="loc_mtz_PowerGenerationAndIndustrialAcquisitionAIn2018Member_43B34A366F31DA395B4916F9E18E3A09" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_4E09C0317FA02CC1550116F9E18E1126" xlink:to="loc_mtz_PowerGenerationAndIndustrialAcquisitionAIn2018Member_43B34A366F31DA395B4916F9E18E3A09" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_PowerGenerationAndIndustrialAcquisitionBIn2018Member" xlink:label="loc_mtz_PowerGenerationAndIndustrialAcquisitionBIn2018Member_5A024DBD4B5085D313DE16F9E18E1143" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_4E09C0317FA02CC1550116F9E18E1126" xlink:to="loc_mtz_PowerGenerationAndIndustrialAcquisitionBIn2018Member_5A024DBD4B5085D313DE16F9E18E1143" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ContingentConsiderationByTypeAxis" xlink:label="loc_us-gaap_ContingentConsiderationByTypeAxis_62E9DBDC73027619E0BF16F9E18D3A3A" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_7F2D024B12858FA1917316F9E18D7851" xlink:to="loc_us-gaap_ContingentConsiderationByTypeAxis_62E9DBDC73027619E0BF16F9E18D3A3A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ContingentConsiderationTypeDomain" xlink:label="loc_us-gaap_ContingentConsiderationTypeDomain_8F18D1494699E7B2AC7416F9E18D94BD_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ContingentConsiderationByTypeAxis_62E9DBDC73027619E0BF16F9E18D3A3A" xlink:to="loc_us-gaap_ContingentConsiderationTypeDomain_8F18D1494699E7B2AC7416F9E18D94BD_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ContingentConsiderationTypeDomain" xlink:label="loc_us-gaap_ContingentConsiderationTypeDomain_8F18D1494699E7B2AC7416F9E18D94BD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ContingentConsiderationByTypeAxis_62E9DBDC73027619E0BF16F9E18D3A3A" xlink:to="loc_us-gaap_ContingentConsiderationTypeDomain_8F18D1494699E7B2AC7416F9E18D94BD" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_EarnoutArrangementsMember" xlink:label="loc_mtz_EarnoutArrangementsMember_4612A50947325C6B95FD16F9E18DCC2F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ContingentConsiderationTypeDomain_8F18D1494699E7B2AC7416F9E18D94BD" xlink:to="loc_mtz_EarnoutArrangementsMember_4612A50947325C6B95FD16F9E18DCC2F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired" xlink:label="loc_us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired_036659C71085A018360A16F9E18EADE1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_F4E9D8E68E6BB0F1326C16F9E18EE579" xlink:to="loc_us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired_036659C71085A018360A16F9E18EADE1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessAcquisitionDescriptionOfAcquiredEntity" xlink:label="loc_us-gaap_BusinessAcquisitionDescriptionOfAcquiredEntity_68337A2C2ACC5146715616F9E18E6557" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_F4E9D8E68E6BB0F1326C16F9E18EE579" xlink:to="loc_us-gaap_BusinessAcquisitionDescriptionOfAcquiredEntity_68337A2C2ACC5146715616F9E18E6557" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PaymentsToAcquireBusinessesGross" xlink:label="loc_us-gaap_PaymentsToAcquireBusinessesGross_8C6D3D7BBE96B1B616F716F9E18EDF6F" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_F4E9D8E68E6BB0F1326C16F9E18EE579" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesGross_8C6D3D7BBE96B1B616F716F9E18EDF6F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessCombinationConsiderationTransferredLiabilitiesIncurred" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferredLiabilitiesIncurred_0C46D685CCA74EC2655F16F9E18EDAF7" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_F4E9D8E68E6BB0F1326C16F9E18EE579" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferredLiabilitiesIncurred_0C46D685CCA74EC2655F16F9E18EDAF7" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.mastec.com/role/GoodwillAndOtherIntangibleAssetsNarrativeDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_GoodwillLineItems" xlink:label="loc_us-gaap_GoodwillLineItems_12C6964F4DBAEA47C8CB121E715F34F7" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfGoodwillTable" xlink:label="loc_us-gaap_ScheduleOfGoodwillTable_CCA317E1DE7D8ED29255121E715EDC6C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_GoodwillLineItems_12C6964F4DBAEA47C8CB121E715F34F7" xlink:to="loc_us-gaap_ScheduleOfGoodwillTable_CCA317E1DE7D8ED29255121E715EDC6C" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BalanceSheetLocationAxis" xlink:label="loc_us-gaap_BalanceSheetLocationAxis_1C39BF0F74F566DC54CB121E715E021E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfGoodwillTable_CCA317E1DE7D8ED29255121E715EDC6C" xlink:to="loc_us-gaap_BalanceSheetLocationAxis_1C39BF0F74F566DC54CB121E715E021E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BalanceSheetLocationDomain" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_4CC8D414D489AED4C15E121E715E66E8_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_1C39BF0F74F566DC54CB121E715E021E" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_4CC8D414D489AED4C15E121E715E66E8_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BalanceSheetLocationDomain" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_4CC8D414D489AED4C15E121E715E66E8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_1C39BF0F74F566DC54CB121E715E021E" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_4CC8D414D489AED4C15E121E715E66E8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_GoodwillMember" xlink:label="loc_us-gaap_GoodwillMember_FAC93822E13829990D35121E715EF0CE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_4CC8D414D489AED4C15E121E715E66E8" xlink:to="loc_us-gaap_GoodwillMember_FAC93822E13829990D35121E715EF0CE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ReserveForImpairmentOfIntangibleAssetsMember" xlink:label="loc_us-gaap_ReserveForImpairmentOfIntangibleAssetsMember_42C5D4CA58687183A9C6121E715EEF6E" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_4CC8D414D489AED4C15E121E715E66E8" xlink:to="loc_us-gaap_ReserveForImpairmentOfIntangibleAssetsMember_42C5D4CA58687183A9C6121E715EEF6E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_GoodwillAcquiredDuringPeriod" xlink:label="loc_us-gaap_GoodwillAcquiredDuringPeriod_8B29AF7FE1ECFC4314E1121E715F61EA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillLineItems_12C6964F4DBAEA47C8CB121E715F34F7" xlink:to="loc_us-gaap_GoodwillAcquiredDuringPeriod_8B29AF7FE1ECFC4314E1121E715F61EA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_GoodwillPurchaseAccountingAdjustments" xlink:label="loc_us-gaap_GoodwillPurchaseAccountingAdjustments_FB33A87194AF955360F0121E715FF685" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillLineItems_12C6964F4DBAEA47C8CB121E715F34F7" xlink:to="loc_us-gaap_GoodwillPurchaseAccountingAdjustments_FB33A87194AF955360F0121E715FF685" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_GoodwillForeignCurrencyTranslationGainLoss" xlink:label="loc_us-gaap_GoodwillForeignCurrencyTranslationGainLoss_C786D67C1D7D31647638121E715F00CF" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillLineItems_12C6964F4DBAEA47C8CB121E715F34F7" xlink:to="loc_us-gaap_GoodwillForeignCurrencyTranslationGainLoss_C786D67C1D7D31647638121E715F00CF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AmortizationOfIntangibleAssets" xlink:label="loc_us-gaap_AmortizationOfIntangibleAssets_4B88D35793FD446F48E9121E715F9125" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillLineItems_12C6964F4DBAEA47C8CB121E715F34F7" xlink:to="loc_us-gaap_AmortizationOfIntangibleAssets_4B88D35793FD446F48E9121E715F9125" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.mastec.com/role/GoodwillAndOtherIntangibleAssetsRollforwardOfOtherIntangibleAssetsDetails" xlink:type="extended">
    <link:loc xlink:href="mtz-20180331.xsd#mtz_IntangibleassetsLineItems" xlink:label="loc_mtz_IntangibleassetsLineItems_FD0571D3A7C88A6F99ACDE8CF1AFB979" xlink:type="locator" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_ScheduleOfIntangibleAssetsTable" xlink:label="loc_mtz_ScheduleOfIntangibleAssetsTable_157E90A45A8D5CDACAB1DE8CF1AFD18B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_mtz_IntangibleassetsLineItems_FD0571D3A7C88A6F99ACDE8CF1AFB979" xlink:to="loc_mtz_ScheduleOfIntangibleAssetsTable_157E90A45A8D5CDACAB1DE8CF1AFD18B" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_8DC3E0C8C504FC218EC3DE8CF1AFE601" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_mtz_ScheduleOfIntangibleAssetsTable_157E90A45A8D5CDACAB1DE8CF1AFD18B" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_8DC3E0C8C504FC218EC3DE8CF1AFE601" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_6BAF37092CB4C9BFF668DE8CF1AFA49C_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_8DC3E0C8C504FC218EC3DE8CF1AFE601" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_6BAF37092CB4C9BFF668DE8CF1AFA49C_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_6BAF37092CB4C9BFF668DE8CF1AFA49C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_8DC3E0C8C504FC218EC3DE8CF1AFE601" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_6BAF37092CB4C9BFF668DE8CF1AFA49C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_TradeNamesMember" xlink:label="loc_us-gaap_TradeNamesMember_BA5E762C57632755306EDE8CF1AF81E1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_6BAF37092CB4C9BFF668DE8CF1AFA49C" xlink:to="loc_us-gaap_TradeNamesMember_BA5E762C57632755306EDE8CF1AF81E1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ContractualRightsMember" xlink:label="loc_us-gaap_ContractualRightsMember_F8C25C40E1DDFC16CA5FDE8CF1AF3893" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_6BAF37092CB4C9BFF668DE8CF1AFA49C" xlink:to="loc_us-gaap_ContractualRightsMember_F8C25C40E1DDFC16CA5FDE8CF1AF3893" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_7824FA0EE922B1628219DE8CF1AF2006" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_mtz_ScheduleOfIntangibleAssetsTable_157E90A45A8D5CDACAB1DE8CF1AFD18B" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_7824FA0EE922B1628219DE8CF1AF2006" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_03BFAF793056281BCB99DE8CF1AF22E9_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_7824FA0EE922B1628219DE8CF1AF2006" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_03BFAF793056281BCB99DE8CF1AF22E9_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_03BFAF793056281BCB99DE8CF1AF22E9" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_7824FA0EE922B1628219DE8CF1AF2006" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_03BFAF793056281BCB99DE8CF1AF22E9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CustomerRelatedIntangibleAssetsMember" xlink:label="loc_us-gaap_CustomerRelatedIntangibleAssetsMember_9F960E15C4AFE3D4DFE3DE8CF1AFA823" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_03BFAF793056281BCB99DE8CF1AF22E9" xlink:to="loc_us-gaap_CustomerRelatedIntangibleAssetsMember_9F960E15C4AFE3D4DFE3DE8CF1AFA823" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_OtherIntangibleAssetsMember" xlink:label="loc_us-gaap_OtherIntangibleAssetsMember_5ABFFEA578B3AA762E88DE8CF1AFC3FE" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_03BFAF793056281BCB99DE8CF1AF22E9" xlink:to="loc_us-gaap_OtherIntangibleAssetsMember_5ABFFEA578B3AA762E88DE8CF1AFC3FE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill_30D397C60208DD979A90DE8CF1B032AF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_mtz_IntangibleassetsLineItems_FD0571D3A7C88A6F99ACDE8CF1AFB979" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill_30D397C60208DD979A90DE8CF1B032AF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsGross" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsGross_2BC88B8FB597FAF8C44DDE8CF1B0B317" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_mtz_IntangibleassetsLineItems_FD0571D3A7C88A6F99ACDE8CF1AFB979" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsGross_2BC88B8FB597FAF8C44DDE8CF1B0B317" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IntangibleAssetsGrossExcludingGoodwill" xlink:label="loc_us-gaap_IntangibleAssetsGrossExcludingGoodwill_BF5177570C01D66A154DDE8CF1B0DF38" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_mtz_IntangibleassetsLineItems_FD0571D3A7C88A6F99ACDE8CF1AFB979" xlink:to="loc_us-gaap_IntangibleAssetsGrossExcludingGoodwill_BF5177570C01D66A154DDE8CF1B0DF38" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_26CF0E15484438753729DE8CF1B039FC" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_mtz_IntangibleassetsLineItems_FD0571D3A7C88A6F99ACDE8CF1AFB979" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_26CF0E15484438753729DE8CF1B039FC" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_IntangibleAssetsExcludingGoodwillRollForward" xlink:label="loc_mtz_IntangibleAssetsExcludingGoodwillRollForward_8E79838FACA0C83B9461DE8CF1B0EEA6" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_mtz_IntangibleassetsLineItems_FD0571D3A7C88A6F99ACDE8CF1AFB979" xlink:to="loc_mtz_IntangibleAssetsExcludingGoodwillRollForward_8E79838FACA0C83B9461DE8CF1B0EEA6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsNet" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_C3382D4DF11E4716E969DE8CF1B02F93" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_mtz_IntangibleAssetsExcludingGoodwillRollForward_8E79838FACA0C83B9461DE8CF1B0EEA6" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNet_C3382D4DF11E4716E969DE8CF1B02F93" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IntangibleAssetsNetExcludingGoodwill" xlink:label="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_7A4B1310EABA54973469DE8CF1B09A15" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_mtz_IntangibleAssetsExcludingGoodwillRollForward_8E79838FACA0C83B9461DE8CF1B0EEA6" xlink:to="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_7A4B1310EABA54973469DE8CF1B09A15" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IndefinitelivedIntangibleAssetsAcquired" xlink:label="loc_us-gaap_IndefinitelivedIntangibleAssetsAcquired_292A1688DFC896600D25DE8CF1B03CEB" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_mtz_IntangibleAssetsExcludingGoodwillRollForward_8E79838FACA0C83B9461DE8CF1B0EEA6" xlink:to="loc_us-gaap_IndefinitelivedIntangibleAssetsAcquired_292A1688DFC896600D25DE8CF1B03CEB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FinitelivedIntangibleAssetsAcquired1" xlink:label="loc_us-gaap_FinitelivedIntangibleAssetsAcquired1_D43D5E15A5AA10F94B93DE8CF1B08299" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_mtz_IntangibleAssetsExcludingGoodwillRollForward_8E79838FACA0C83B9461DE8CF1B0EEA6" xlink:to="loc_us-gaap_FinitelivedIntangibleAssetsAcquired1_D43D5E15A5AA10F94B93DE8CF1B08299" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_IntangibleAssetsAcquiredGrossExcludingGoodwill" xlink:label="loc_mtz_IntangibleAssetsAcquiredGrossExcludingGoodwill_74E53D49C5E9B98C47C8DE8CF1B08344" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_mtz_IntangibleAssetsExcludingGoodwillRollForward_8E79838FACA0C83B9461DE8CF1B0EEA6" xlink:to="loc_mtz_IntangibleAssetsAcquiredGrossExcludingGoodwill_74E53D49C5E9B98C47C8DE8CF1B08344" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IndefiniteLivedIntangibleAssetsPurchaseAccountingAdjustments" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsPurchaseAccountingAdjustments_44815EB3908B9362E6F3DEF6A5B794C8" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_mtz_IntangibleAssetsExcludingGoodwillRollForward_8E79838FACA0C83B9461DE8CF1B0EEA6" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsPurchaseAccountingAdjustments_44815EB3908B9362E6F3DEF6A5B794C8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsPurchaseAccountingAdjustments" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsPurchaseAccountingAdjustments_3B5A99FA3B5CB932ACF0DF072AE0A64B" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_mtz_IntangibleAssetsExcludingGoodwillRollForward_8E79838FACA0C83B9461DE8CF1B0EEA6" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsPurchaseAccountingAdjustments_3B5A99FA3B5CB932ACF0DF072AE0A64B" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_IntangibleAssetsExcludingGoodwillPurchaseAccountingAdjustments" xlink:label="loc_mtz_IntangibleAssetsExcludingGoodwillPurchaseAccountingAdjustments_C3C528948468972DFBB6DF12672A0D78" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_mtz_IntangibleAssetsExcludingGoodwillRollForward_8E79838FACA0C83B9461DE8CF1B0EEA6" xlink:to="loc_mtz_IntangibleAssetsExcludingGoodwillPurchaseAccountingAdjustments_C3C528948468972DFBB6DF12672A0D78" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AmortizationOfIntangibleAssets" xlink:label="loc_us-gaap_AmortizationOfIntangibleAssets_75BC231A13A92E9BBC76DE8CF1B0B893" xlink:type="locator" />
    <link:definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_mtz_IntangibleAssetsExcludingGoodwillRollForward_8E79838FACA0C83B9461DE8CF1B0EEA6" xlink:to="loc_us-gaap_AmortizationOfIntangibleAssets_75BC231A13A92E9BBC76DE8CF1B0B893" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IndefiniteLivedIntangibleAssetsForeignCurrencyTranslationGainLoss" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsForeignCurrencyTranslationGainLoss_D31EE5530BCFFA82D786DE8CF1B0E201" xlink:type="locator" />
    <link:definitionArc order="11" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_mtz_IntangibleAssetsExcludingGoodwillRollForward_8E79838FACA0C83B9461DE8CF1B0EEA6" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsForeignCurrencyTranslationGainLoss_D31EE5530BCFFA82D786DE8CF1B0E201" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsForeignCurrencyTranslationGainLoss" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsForeignCurrencyTranslationGainLoss_DE9CE91C25EE68A27235DE8CF1B18DE3" xlink:type="locator" />
    <link:definitionArc order="12" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_mtz_IntangibleAssetsExcludingGoodwillRollForward_8E79838FACA0C83B9461DE8CF1B0EEA6" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsForeignCurrencyTranslationGainLoss_DE9CE91C25EE68A27235DE8CF1B18DE3" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_IntangibleAssetsGrossExcludingGoodwillTranslationAdjustments" xlink:label="loc_mtz_IntangibleAssetsGrossExcludingGoodwillTranslationAdjustments_6E0BF9CE6449470FCB40DE8CF1B16CF2" xlink:type="locator" />
    <link:definitionArc order="13" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_mtz_IntangibleAssetsExcludingGoodwillRollForward_8E79838FACA0C83B9461DE8CF1B0EEA6" xlink:to="loc_mtz_IntangibleAssetsGrossExcludingGoodwillTranslationAdjustments_6E0BF9CE6449470FCB40DE8CF1B16CF2" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.mastec.com/role/GoodwillAndOtherIntangibleAssetsScheduleOfConsiderationPaidAndNetAssetsAcquiredBusinessCombinationsDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessAcquisitionLineItems" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_E052CC23A2F10FD7029E025D435C0C9F" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_E2555E73CA9AAD413BA3025D43560660" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_E052CC23A2F10FD7029E025D435C0C9F" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_E2555E73CA9AAD413BA3025D43560660" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessAcquisitionAxis" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_A5A33242AABB862ACE4F025D4356794D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_E2555E73CA9AAD413BA3025D43560660" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_A5A33242AABB862ACE4F025D4356794D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_7297D76DC4271A7F6263025D435BEAD9_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_A5A33242AABB862ACE4F025D4356794D" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_7297D76DC4271A7F6263025D435BEAD9_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_7297D76DC4271A7F6263025D435BEAD9" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_A5A33242AABB862ACE4F025D4356794D" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_7297D76DC4271A7F6263025D435BEAD9" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_A2017AcquisitionsMember" xlink:label="loc_mtz_A2017AcquisitionsMember_3799CA100EAD9330873E025D435B4256" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_7297D76DC4271A7F6263025D435BEAD9" xlink:to="loc_mtz_A2017AcquisitionsMember_3799CA100EAD9330873E025D435B4256" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ContingentConsiderationByTypeAxis" xlink:label="loc_us-gaap_ContingentConsiderationByTypeAxis_C160F71DF0F3D3D19996025D435BC675" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_E2555E73CA9AAD413BA3025D43560660" xlink:to="loc_us-gaap_ContingentConsiderationByTypeAxis_C160F71DF0F3D3D19996025D435BC675" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ContingentConsiderationTypeDomain" xlink:label="loc_us-gaap_ContingentConsiderationTypeDomain_3443042894E91B92FECB025D435C4EE4_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ContingentConsiderationByTypeAxis_C160F71DF0F3D3D19996025D435BC675" xlink:to="loc_us-gaap_ContingentConsiderationTypeDomain_3443042894E91B92FECB025D435C4EE4_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ContingentConsiderationTypeDomain" xlink:label="loc_us-gaap_ContingentConsiderationTypeDomain_3443042894E91B92FECB025D435C4EE4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ContingentConsiderationByTypeAxis_C160F71DF0F3D3D19996025D435BC675" xlink:to="loc_us-gaap_ContingentConsiderationTypeDomain_3443042894E91B92FECB025D435C4EE4" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_EarnoutArrangementsMember" xlink:label="loc_mtz_EarnoutArrangementsMember_8406D8D52684FED0E8D5025D435C12EC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ContingentConsiderationTypeDomain_3443042894E91B92FECB025D435C4EE4" xlink:to="loc_mtz_EarnoutArrangementsMember_8406D8D52684FED0E8D5025D435C12EC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessCombinationConsiderationTransferredAbstract" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferredAbstract_1966B15A0A499851776D025D435C44AD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_E052CC23A2F10FD7029E025D435C0C9F" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferredAbstract_1966B15A0A499851776D025D435C44AD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PaymentsToAcquireBusinessesGross" xlink:label="loc_us-gaap_PaymentsToAcquireBusinessesGross_854A9AE51F6AAC14808C025D435C6DAA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationConsiderationTransferredAbstract_1966B15A0A499851776D025D435C44AD" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesGross_854A9AE51F6AAC14808C025D435C6DAA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessCombinationConsiderationTransferredLiabilitiesIncurred" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferredLiabilitiesIncurred_FD7F7298CD19D9AB7B87025D435CB310" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationConsiderationTransferredAbstract_1966B15A0A499851776D025D435C44AD" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferredLiabilitiesIncurred_FD7F7298CD19D9AB7B87025D435CB310" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessCombinationConsiderationTransferred1" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferred1_5ABDED955E65C8E26A32025D435C9D64" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationConsiderationTransferredAbstract_1966B15A0A499851776D025D435C44AD" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferred1_5ABDED955E65C8E26A32025D435C9D64" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_CEF638247CBCFE57192D025D435CC9A3" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_E052CC23A2F10FD7029E025D435C0C9F" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_CEF638247CBCFE57192D025D435CC9A3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssets" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssets_2FCEED1150E576731A28025D435CFF4B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_CEF638247CBCFE57192D025D435CC9A3" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssets_2FCEED1150E576731A28025D435CFF4B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents_73FD33E098E3ECF8F469025D435C48D1" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_CEF638247CBCFE57192D025D435CC9A3" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents_73FD33E098E3ECF8F469025D435C48D1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment_771D2A8610B966CDA05F025D435C24C0" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_CEF638247CBCFE57192D025D435CC9A3" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment_771D2A8610B966CDA05F025D435C24C0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles_B7C7E67F66BBC10F8008025D435CB056" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_CEF638247CBCFE57192D025D435CC9A3" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles_B7C7E67F66BBC10F8008025D435CB056" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilities" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilities_2680422C344D818CEB65025D435DAE04" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_CEF638247CBCFE57192D025D435CC9A3" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilities_2680422C344D818CEB65025D435DAE04" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesLongTermDebt" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesLongTermDebt_A8422164D00BF31FFC01025D435D5E21" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_CEF638247CBCFE57192D025D435CC9A3" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesLongTermDebt_A8422164D00BF31FFC01025D435D5E21" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredTaxLiabilities" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredTaxLiabilities_F67F3AE3DFC00F233A56025D435D7806" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_CEF638247CBCFE57192D025D435CC9A3" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredTaxLiabilities_F67F3AE3DFC00F233A56025D435D7806" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_C85A3ADD5AA4E1E546CE025D435D5630" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_CEF638247CBCFE57192D025D435CC9A3" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_C85A3ADD5AA4E1E546CE025D435D5630" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_Goodwill" xlink:label="loc_us-gaap_Goodwill_7A5255773CF7A7CA98F3025D435D6BA6" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_CEF638247CBCFE57192D025D435CC9A3" xlink:to="loc_us-gaap_Goodwill_7A5255773CF7A7CA98F3025D435D6BA6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet_FA1CEEA2B875046F49F0025D435D6B2E" xlink:type="locator" />
    <link:definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_CEF638247CBCFE57192D025D435CC9A3" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet_FA1CEEA2B875046F49F0025D435D6B2E" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.mastec.com/role/GoodwillAndOtherIntangibleAssetsScheduleOfGoodwillBySegmentDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_GoodwillLineItems" xlink:label="loc_us-gaap_GoodwillLineItems_DBB677D4A371543BB3D36807CD82A7B9" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfGoodwillTable" xlink:label="loc_us-gaap_ScheduleOfGoodwillTable_64328A270AC354E9B062196FD8DB13E9" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_GoodwillLineItems_DBB677D4A371543BB3D36807CD82A7B9" xlink:to="loc_us-gaap_ScheduleOfGoodwillTable_64328A270AC354E9B062196FD8DB13E9" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_StatementBusinessSegmentsAxis" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_C7A9893D0AC758658753D206943E64BB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfGoodwillTable_64328A270AC354E9B062196FD8DB13E9" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_C7A9893D0AC758658753D206943E64BB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SegmentDomain" xlink:label="loc_us-gaap_SegmentDomain_D841E25FE9CE49C1AB2605C9BE0B5A78_8FF700ECD19F568F86EB052BB273C9DB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_C7A9893D0AC758658753D206943E64BB" xlink:to="loc_us-gaap_SegmentDomain_D841E25FE9CE49C1AB2605C9BE0B5A78_8FF700ECD19F568F86EB052BB273C9DB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SegmentDomain" xlink:label="loc_us-gaap_SegmentDomain_A2DD484476D5548CA3A4C112D689469B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_C7A9893D0AC758658753D206943E64BB" xlink:to="loc_us-gaap_SegmentDomain_A2DD484476D5548CA3A4C112D689469B" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_CommunicationsMember" xlink:label="loc_mtz_CommunicationsMember_0E2B5BA5B1A85EA89CA81A20E16DE348" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_A2DD484476D5548CA3A4C112D689469B" xlink:to="loc_mtz_CommunicationsMember_0E2B5BA5B1A85EA89CA81A20E16DE348" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_OilAndGasMember" xlink:label="loc_mtz_OilAndGasMember_C74F6C2E6A305515B91872E85753A885" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_A2DD484476D5548CA3A4C112D689469B" xlink:to="loc_mtz_OilAndGasMember_C74F6C2E6A305515B91872E85753A885" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_ElectricalTransmissionMember" xlink:label="loc_mtz_ElectricalTransmissionMember_CF99053E05D1578FA9DAE1CDD7FAE665" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_A2DD484476D5548CA3A4C112D689469B" xlink:to="loc_mtz_ElectricalTransmissionMember_CF99053E05D1578FA9DAE1CDD7FAE665" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_PowerGenerationAndIndustrialMember" xlink:label="loc_mtz_PowerGenerationAndIndustrialMember_0EF76508C57F5EA4AC57B6AD0EC10CB1" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_A2DD484476D5548CA3A4C112D689469B" xlink:to="loc_mtz_PowerGenerationAndIndustrialMember_0EF76508C57F5EA4AC57B6AD0EC10CB1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_GoodwillGross" xlink:label="loc_us-gaap_GoodwillGross_855E0324B63854E192C87DE82A0831BE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillLineItems_DBB677D4A371543BB3D36807CD82A7B9" xlink:to="loc_us-gaap_GoodwillGross_855E0324B63854E192C87DE82A0831BE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_GoodwillImpairedAccumulatedImpairmentLoss" xlink:label="loc_us-gaap_GoodwillImpairedAccumulatedImpairmentLoss_BEFF9074AFCA523AAB0645EF7F8294F3" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillLineItems_DBB677D4A371543BB3D36807CD82A7B9" xlink:to="loc_us-gaap_GoodwillImpairedAccumulatedImpairmentLoss_BEFF9074AFCA523AAB0645EF7F8294F3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_Goodwill" xlink:label="loc_us-gaap_Goodwill_9497AED7A493591D90882CB43B1A5536" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillLineItems_DBB677D4A371543BB3D36807CD82A7B9" xlink:to="loc_us-gaap_Goodwill_9497AED7A493591D90882CB43B1A5536" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.mastec.com/role/GoodwillAndOtherIntangibleAssetsTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.mastec.com/role/GoodwillAndOtherIntangibleAssetsUnauditedProFormaFinancialInformationNarrativeDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.mastec.com/role/IncomeTaxes" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.mastec.com/role/IncomeTaxesNarrativeDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.mastec.com/role/LeaseObligations" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.mastec.com/role/LeaseObligationsCapitalLeasesNarrativeDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CapitalLeasedAssetsLineItems" xlink:label="loc_us-gaap_CapitalLeasedAssetsLineItems_B1946D3C090F5F309DD52487E6B555FE" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfCapitalLeasedAsssetsTable" xlink:label="loc_us-gaap_ScheduleOfCapitalLeasedAsssetsTable_D3AB540DA97B5D40AAA97008DDA8F359" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_CapitalLeasedAssetsLineItems_B1946D3C090F5F309DD52487E6B555FE" xlink:to="loc_us-gaap_ScheduleOfCapitalLeasedAsssetsTable_D3AB540DA97B5D40AAA97008DDA8F359" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BalanceSheetLocationAxis" xlink:label="loc_us-gaap_BalanceSheetLocationAxis_264B37836225508F916D0D5CF7B8C84D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfCapitalLeasedAsssetsTable_D3AB540DA97B5D40AAA97008DDA8F359" xlink:to="loc_us-gaap_BalanceSheetLocationAxis_264B37836225508F916D0D5CF7B8C84D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BalanceSheetLocationDomain" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_8E5E8A9E3C69CF1CD6B005C9BC65DF66_8FF700ECD19F568F86EB052BB273C9DB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_264B37836225508F916D0D5CF7B8C84D" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_8E5E8A9E3C69CF1CD6B005C9BC65DF66_8FF700ECD19F568F86EB052BB273C9DB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BalanceSheetLocationDomain" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_736F65ED8FE755D2897425951104E316" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_264B37836225508F916D0D5CF7B8C84D" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_736F65ED8FE755D2897425951104E316" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PropertyPlantAndEquipmentMember" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentMember_84290C4874C55674A1D7898756EFE7C4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_736F65ED8FE755D2897425951104E316" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentMember_84290C4874C55674A1D7898756EFE7C4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CapitalLeasedAssetsGross" xlink:label="loc_us-gaap_CapitalLeasedAssetsGross_B5DBE73D853F53EDADA7B8C0E955FBE7" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalLeasedAssetsLineItems_B1946D3C090F5F309DD52487E6B555FE" xlink:to="loc_us-gaap_CapitalLeasedAssetsGross_B5DBE73D853F53EDADA7B8C0E955FBE7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CapitalLeasesBalanceSheetAssetsByMajorClassNet" xlink:label="loc_us-gaap_CapitalLeasesBalanceSheetAssetsByMajorClassNet_17667A04BC8E5E7B8C6E5168D17B32BB" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalLeasedAssetsLineItems_B1946D3C090F5F309DD52487E6B555FE" xlink:to="loc_us-gaap_CapitalLeasesBalanceSheetAssetsByMajorClassNet_17667A04BC8E5E7B8C6E5168D17B32BB" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.mastec.com/role/LeaseObligationsOperatingLeasesNarrativeDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_OperatingLeasedAssetsLineItems" xlink:label="loc_us-gaap_OperatingLeasedAssetsLineItems_E552FE9096255E1FB728DE4FC135C571" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfOperatingLeasedAssetsTable" xlink:label="loc_us-gaap_ScheduleOfOperatingLeasedAssetsTable_F73C9411347B5F41A66F8FA8976E8783" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_OperatingLeasedAssetsLineItems_E552FE9096255E1FB728DE4FC135C571" xlink:to="loc_us-gaap_ScheduleOfOperatingLeasedAssetsTable_F73C9411347B5F41A66F8FA8976E8783" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LeaseArrangementTypeAxis" xlink:label="loc_us-gaap_LeaseArrangementTypeAxis_2D7EF2A040105C8C9921E6967F317A08" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfOperatingLeasedAssetsTable_F73C9411347B5F41A66F8FA8976E8783" xlink:to="loc_us-gaap_LeaseArrangementTypeAxis_2D7EF2A040105C8C9921E6967F317A08" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LeaseArrangementTypeDomain" xlink:label="loc_us-gaap_LeaseArrangementTypeDomain_4CF08619B26C6BF9E5C3DDBCA4B27A6E_8FF700ECD19F568F86EB052BB273C9DB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LeaseArrangementTypeAxis_2D7EF2A040105C8C9921E6967F317A08" xlink:to="loc_us-gaap_LeaseArrangementTypeDomain_4CF08619B26C6BF9E5C3DDBCA4B27A6E_8FF700ECD19F568F86EB052BB273C9DB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LeaseArrangementTypeDomain" xlink:label="loc_us-gaap_LeaseArrangementTypeDomain_0D76D39708E25F62BC2ECBEFBF75CF33" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LeaseArrangementTypeAxis_2D7EF2A040105C8C9921E6967F317A08" xlink:to="loc_us-gaap_LeaseArrangementTypeDomain_0D76D39708E25F62BC2ECBEFBF75CF33" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_LeaseTermInExcessOfOneYearMember" xlink:label="loc_mtz_LeaseTermInExcessOfOneYearMember_AB3EFB5C511B54DEBCD26CC84362ADE5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LeaseArrangementTypeDomain_0D76D39708E25F62BC2ECBEFBF75CF33" xlink:to="loc_mtz_LeaseTermInExcessOfOneYearMember_AB3EFB5C511B54DEBCD26CC84362ADE5" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_LeaseTermLessThanOneYearMember" xlink:label="loc_mtz_LeaseTermLessThanOneYearMember_366C6BD2ABBE5A9398E1068FF778CA78" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LeaseArrangementTypeDomain_0D76D39708E25F62BC2ECBEFBF75CF33" xlink:to="loc_mtz_LeaseTermLessThanOneYearMember_366C6BD2ABBE5A9398E1068FF778CA78" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RangeAxis" xlink:label="loc_us-gaap_RangeAxis_F29A7D8C964E5C73A0C52B6C443E4C8D" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfOperatingLeasedAssetsTable_F73C9411347B5F41A66F8FA8976E8783" xlink:to="loc_us-gaap_RangeAxis_F29A7D8C964E5C73A0C52B6C443E4C8D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RangeMember" xlink:label="loc_us-gaap_RangeMember_A7841782AF68B3E42E23DDBCA4B2F3D3_8FF700ECD19F568F86EB052BB273C9DB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RangeAxis_F29A7D8C964E5C73A0C52B6C443E4C8D" xlink:to="loc_us-gaap_RangeMember_A7841782AF68B3E42E23DDBCA4B2F3D3_8FF700ECD19F568F86EB052BB273C9DB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RangeMember" xlink:label="loc_us-gaap_RangeMember_2C5313226A4B51D4B6D1F0A15F3F37D6" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RangeAxis_F29A7D8C964E5C73A0C52B6C443E4C8D" xlink:to="loc_us-gaap_RangeMember_2C5313226A4B51D4B6D1F0A15F3F37D6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_MinimumMember" xlink:label="loc_us-gaap_MinimumMember_659F398704A8534294856547A06E7358" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RangeMember_2C5313226A4B51D4B6D1F0A15F3F37D6" xlink:to="loc_us-gaap_MinimumMember_659F398704A8534294856547A06E7358" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_MaximumMember" xlink:label="loc_us-gaap_MaximumMember_DD70DE61E0515745880C838FCB993FCE" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RangeMember_2C5313226A4B51D4B6D1F0A15F3F37D6" xlink:to="loc_us-gaap_MaximumMember_DD70DE61E0515745880C838FCB993FCE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LesseeLeasingArrangementsOperatingLeasesTermOfContract" xlink:label="loc_us-gaap_LesseeLeasingArrangementsOperatingLeasesTermOfContract_29F58ACEAAD55336BAAC5D47E86D2EB5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLeasedAssetsLineItems_E552FE9096255E1FB728DE4FC135C571" xlink:to="loc_us-gaap_LesseeLeasingArrangementsOperatingLeasesTermOfContract_29F58ACEAAD55336BAAC5D47E86D2EB5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_OperatingLeasesRentExpenseNet" xlink:label="loc_us-gaap_OperatingLeasesRentExpenseNet_625C9064228C543DAF3A83D11A0B98A1" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLeasedAssetsLineItems_E552FE9096255E1FB728DE4FC135C571" xlink:to="loc_us-gaap_OperatingLeasesRentExpenseNet_625C9064228C543DAF3A83D11A0B98A1" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.mastec.com/role/OtherRetirementPlans" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.mastec.com/role/OtherRetirementPlansNarrativeDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.mastec.com/role/OtherRetirementPlansScheduleOfCoveredEmployeesAndContributionsMultiemployerPlansDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_MultiemployerPlansLineItems" xlink:label="loc_us-gaap_MultiemployerPlansLineItems_D5783BD1518E562B8EAE7E3822DE16F2" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfMultiemployerPlansTable" xlink:label="loc_us-gaap_ScheduleOfMultiemployerPlansTable_A153F48CA92256C49453027B6252A525" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_MultiemployerPlansLineItems_D5783BD1518E562B8EAE7E3822DE16F2" xlink:to="loc_us-gaap_ScheduleOfMultiemployerPlansTable_A153F48CA92256C49453027B6252A525" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConcentrationRiskByBenchmarkAxis" xlink:label="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_DC15AC82F6325FD8B44362EC341469EC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfMultiemployerPlansTable_A153F48CA92256C49453027B6252A525" xlink:to="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_DC15AC82F6325FD8B44362EC341469EC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConcentrationRiskBenchmarkDomain" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_C8A6A180E4AF8926AE6D05C9BDDBB395_8FF700ECD19F568F86EB052BB273C9DB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_DC15AC82F6325FD8B44362EC341469EC" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_C8A6A180E4AF8926AE6D05C9BDDBB395_8FF700ECD19F568F86EB052BB273C9DB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConcentrationRiskBenchmarkDomain" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_38A1E637686855D1995F341D52F656A0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_DC15AC82F6325FD8B44362EC341469EC" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_38A1E637686855D1995F341D52F656A0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_WorkforceSubjectToCollectiveBargainingArrangementsMember" xlink:label="loc_us-gaap_WorkforceSubjectToCollectiveBargainingArrangementsMember_6EE767009A6355D89C0B93089CA118DC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_38A1E637686855D1995F341D52F656A0" xlink:to="loc_us-gaap_WorkforceSubjectToCollectiveBargainingArrangementsMember_6EE767009A6355D89C0B93089CA118DC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConcentrationRiskByTypeAxis" xlink:label="loc_us-gaap_ConcentrationRiskByTypeAxis_9235F9F916215F0F81886AB21E3DB2CE" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfMultiemployerPlansTable_A153F48CA92256C49453027B6252A525" xlink:to="loc_us-gaap_ConcentrationRiskByTypeAxis_9235F9F916215F0F81886AB21E3DB2CE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConcentrationRiskTypeDomain" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_C4F8D4C12FD0E774A42F05C9BDDB4AC2_8FF700ECD19F568F86EB052BB273C9DB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_9235F9F916215F0F81886AB21E3DB2CE" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_C4F8D4C12FD0E774A42F05C9BDDB4AC2_8FF700ECD19F568F86EB052BB273C9DB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConcentrationRiskTypeDomain" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_FF31F39A2BB35218B490E40E03F08BAC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_9235F9F916215F0F81886AB21E3DB2CE" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_FF31F39A2BB35218B490E40E03F08BAC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_UnionizedEmployeesConcentrationRiskMember" xlink:label="loc_us-gaap_UnionizedEmployeesConcentrationRiskMember_695E876794655CC583635D3EC9081C40" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_FF31F39A2BB35218B490E40E03F08BAC" xlink:to="loc_us-gaap_UnionizedEmployeesConcentrationRiskMember_695E876794655CC583635D3EC9081C40" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RangeAxis" xlink:label="loc_us-gaap_RangeAxis_C3E16064881F500C91557F38D643F9E9" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfMultiemployerPlansTable_A153F48CA92256C49453027B6252A525" xlink:to="loc_us-gaap_RangeAxis_C3E16064881F500C91557F38D643F9E9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RangeMember" xlink:label="loc_us-gaap_RangeMember_21D8C2446D14A53DE7BE05C9BDDC7E37_8FF700ECD19F568F86EB052BB273C9DB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RangeAxis_C3E16064881F500C91557F38D643F9E9" xlink:to="loc_us-gaap_RangeMember_21D8C2446D14A53DE7BE05C9BDDC7E37_8FF700ECD19F568F86EB052BB273C9DB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RangeMember" xlink:label="loc_us-gaap_RangeMember_D8D73318C1375C019E072155C4C0BA8B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RangeAxis_C3E16064881F500C91557F38D643F9E9" xlink:to="loc_us-gaap_RangeMember_D8D73318C1375C019E072155C4C0BA8B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_MinimumMember" xlink:label="loc_us-gaap_MinimumMember_9BD8C495B4075D2A969214E70810A5E8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RangeMember_D8D73318C1375C019E072155C4C0BA8B" xlink:to="loc_us-gaap_MinimumMember_9BD8C495B4075D2A969214E70810A5E8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_MaximumMember" xlink:label="loc_us-gaap_MaximumMember_6D5D07ED17B459D59CF2E1C46B665FFF" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RangeMember_D8D73318C1375C019E072155C4C0BA8B" xlink:to="loc_us-gaap_MaximumMember_6D5D07ED17B459D59CF2E1C46B665FFF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_MultiemployerPlanTypeAxis" xlink:label="loc_us-gaap_MultiemployerPlanTypeAxis_1BC060B2D8D553C0886E56B2CD41C25A" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfMultiemployerPlansTable_A153F48CA92256C49453027B6252A525" xlink:to="loc_us-gaap_MultiemployerPlanTypeAxis_1BC060B2D8D553C0886E56B2CD41C25A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_MultiemployerPlansTypeDomain" xlink:label="loc_us-gaap_MultiemployerPlansTypeDomain_032A66167F0AE133626D05C9BDDC60E2_8FF700ECD19F568F86EB052BB273C9DB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_MultiemployerPlanTypeAxis_1BC060B2D8D553C0886E56B2CD41C25A" xlink:to="loc_us-gaap_MultiemployerPlansTypeDomain_032A66167F0AE133626D05C9BDDC60E2_8FF700ECD19F568F86EB052BB273C9DB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_MultiemployerPlansTypeDomain" xlink:label="loc_us-gaap_MultiemployerPlansTypeDomain_E23AE4391F56513789A5352455E89390" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_MultiemployerPlanTypeAxis_1BC060B2D8D553C0886E56B2CD41C25A" xlink:to="loc_us-gaap_MultiemployerPlansTypeDomain_E23AE4391F56513789A5352455E89390" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_MultiemployerPlansPensionMember" xlink:label="loc_us-gaap_MultiemployerPlansPensionMember_3A5B33AEE29559E79B8DBE2BADEDE2F5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MultiemployerPlansTypeDomain_E23AE4391F56513789A5352455E89390" xlink:to="loc_us-gaap_MultiemployerPlansPensionMember_3A5B33AEE29559E79B8DBE2BADEDE2F5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_MultiemployerPlansPostretirementBenefitMember" xlink:label="loc_us-gaap_MultiemployerPlansPostretirementBenefitMember_CBDE1AEBDC76559BB8E15E6C820A2442" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MultiemployerPlansTypeDomain_E23AE4391F56513789A5352455E89390" xlink:to="loc_us-gaap_MultiemployerPlansPostretirementBenefitMember_CBDE1AEBDC76559BB8E15E6C820A2442" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_EntityNumberOfEmployeesDuringPeriod" xlink:label="loc_mtz_EntityNumberOfEmployeesDuringPeriod_4DF88B2315F25109B0402D1CC0637A24" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MultiemployerPlansLineItems_D5783BD1518E562B8EAE7E3822DE16F2" xlink:to="loc_mtz_EntityNumberOfEmployeesDuringPeriod_4DF88B2315F25109B0402D1CC0637A24" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_MultiemployerPlanContributionsByEmployer" xlink:label="loc_us-gaap_MultiemployerPlanContributionsByEmployer_0255C4E346F1530D949C6AA68167EDBA" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MultiemployerPlansLineItems_D5783BD1518E562B8EAE7E3822DE16F2" xlink:to="loc_us-gaap_MultiemployerPlanContributionsByEmployer_0255C4E346F1530D949C6AA68167EDBA" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.mastec.com/role/OtherRetirementPlansTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.mastec.com/role/PropertyAndEquipmentNet" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.mastec.com/role/PropertyAndEquipmentNetNarrativeDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PropertyPlantAndEquipmentLineItems" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentLineItems_A46AABBDB85254EDBE0B5A21F32F24E1" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfPropertyPlantAndEquipmentTable" xlink:label="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_734401943ABD59E9A82306605B74F8AC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_A46AABBDB85254EDBE0B5A21F32F24E1" xlink:to="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_734401943ABD59E9A82306605B74F8AC" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueByAssetClassAxis" xlink:label="loc_us-gaap_FairValueByAssetClassAxis_F1C1818DDA4E50A3926AA77927BBE07B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_734401943ABD59E9A82306605B74F8AC" xlink:to="loc_us-gaap_FairValueByAssetClassAxis_F1C1818DDA4E50A3926AA77927BBE07B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_93E0B1D44B0514CA687805C9BDC4522C_8FF700ECD19F568F86EB052BB273C9DB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByAssetClassAxis_F1C1818DDA4E50A3926AA77927BBE07B" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_93E0B1D44B0514CA687805C9BDC4522C_8FF700ECD19F568F86EB052BB273C9DB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_C01191A6C5DD596B801D4986BE9EF264" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByAssetClassAxis_F1C1818DDA4E50A3926AA77927BBE07B" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_C01191A6C5DD596B801D4986BE9EF264" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PropertyPlantAndEquipmentMember" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentMember_9CC825EA4B2759EC94FDA201C89DEA89" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_C01191A6C5DD596B801D4986BE9EF264" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentMember_9CC825EA4B2759EC94FDA201C89DEA89" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CapitalizedComputerSoftwareGross" xlink:label="loc_us-gaap_CapitalizedComputerSoftwareGross_0A6A64EB63B75AE9A87F681AA070E7CE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_A46AABBDB85254EDBE0B5A21F32F24E1" xlink:to="loc_us-gaap_CapitalizedComputerSoftwareGross_0A6A64EB63B75AE9A87F681AA070E7CE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CapitalizedComputerSoftwareNet" xlink:label="loc_us-gaap_CapitalizedComputerSoftwareNet_971D09E0F8FD5B8EB0E3FE9457039625" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_A46AABBDB85254EDBE0B5A21F32F24E1" xlink:to="loc_us-gaap_CapitalizedComputerSoftwareNet_971D09E0F8FD5B8EB0E3FE9457039625" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DepreciationDepletionAndAmortization" xlink:label="loc_us-gaap_DepreciationDepletionAndAmortization_F9607D067C895A59A4AA4425FB00C5EB" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_A46AABBDB85254EDBE0B5A21F32F24E1" xlink:to="loc_us-gaap_DepreciationDepletionAndAmortization_F9607D067C895A59A4AA4425FB00C5EB" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.mastec.com/role/PropertyAndEquipmentNetScheduleOfPropertyAndEquipmentNetDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PropertyPlantAndEquipmentLineItems" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentLineItems_2CBB824AFC62526B9C7D33F5DE58CEFE" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfPropertyPlantAndEquipmentTable" xlink:label="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_4BDCFA5AD1B15EAE9616F1DA8F6F82B9" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_2CBB824AFC62526B9C7D33F5DE58CEFE" xlink:to="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_4BDCFA5AD1B15EAE9616F1DA8F6F82B9" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_183CAB1BC51D56CBA4A1061405824A2B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_4BDCFA5AD1B15EAE9616F1DA8F6F82B9" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_183CAB1BC51D56CBA4A1061405824A2B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_1B546F930A69A53D6A4E05C9BCD95E89_8FF700ECD19F568F86EB052BB273C9DB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_183CAB1BC51D56CBA4A1061405824A2B" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_1B546F930A69A53D6A4E05C9BCD95E89_8FF700ECD19F568F86EB052BB273C9DB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_DC22A909A61259DF8A46B30535B4EEA1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_183CAB1BC51D56CBA4A1061405824A2B" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_DC22A909A61259DF8A46B30535B4EEA1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LandMember" xlink:label="loc_us-gaap_LandMember_D3384AC163D151EFB28E0223A85DB987" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_DC22A909A61259DF8A46B30535B4EEA1" xlink:to="loc_us-gaap_LandMember_D3384AC163D151EFB28E0223A85DB987" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BuildingAndBuildingImprovementsMember" xlink:label="loc_us-gaap_BuildingAndBuildingImprovementsMember_4986466DDF5E5D9CB6A1B621EDF62606" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_DC22A909A61259DF8A46B30535B4EEA1" xlink:to="loc_us-gaap_BuildingAndBuildingImprovementsMember_4986466DDF5E5D9CB6A1B621EDF62606" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_MachineryAndEquipmentMember" xlink:label="loc_us-gaap_MachineryAndEquipmentMember_0AE53706255B5963BD4E7A5A6BC4B137" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_DC22A909A61259DF8A46B30535B4EEA1" xlink:to="loc_us-gaap_MachineryAndEquipmentMember_0AE53706255B5963BD4E7A5A6BC4B137" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FurnitureAndFixturesMember" xlink:label="loc_us-gaap_FurnitureAndFixturesMember_CB3AD912EF1854538A4E584B42461105" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_DC22A909A61259DF8A46B30535B4EEA1" xlink:to="loc_us-gaap_FurnitureAndFixturesMember_CB3AD912EF1854538A4E584B42461105" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConstructionInProgressMember" xlink:label="loc_us-gaap_ConstructionInProgressMember_779CE4D52BD2517D81307FF26501BBEB" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_DC22A909A61259DF8A46B30535B4EEA1" xlink:to="loc_us-gaap_ConstructionInProgressMember_779CE4D52BD2517D81307FF26501BBEB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PropertyPlantAndEquipmentGross" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentGross_54422215BEFC5B4E97CBFAEC40BD2049" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_2CBB824AFC62526B9C7D33F5DE58CEFE" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentGross_54422215BEFC5B4E97CBFAEC40BD2049" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment" xlink:label="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_B2FC28DBD9F45F37A3C7C0717A040974" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_2CBB824AFC62526B9C7D33F5DE58CEFE" xlink:to="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_B2FC28DBD9F45F37A3C7C0717A040974" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PropertyPlantAndEquipmentNet" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_40AC1047BE3551D992C93D309D30620C" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_2CBB824AFC62526B9C7D33F5DE58CEFE" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_40AC1047BE3551D992C93D309D30620C" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.mastec.com/role/PropertyAndEquipmentNetTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.mastec.com/role/RelatedPartyTransactions" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.mastec.com/role/RelatedPartyTransactionsCciNarrativeDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionLineItems" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_7C7504F72EF2EEF04C81F3F0A735EB63" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_2D54CEB1E672EF5161A6F3F0A7340760" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_7C7504F72EF2EEF04C81F3F0A735EB63" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_2D54CEB1E672EF5161A6F3F0A7340760" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_F5D411152B32C70705D9F3F0A734F406" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_2D54CEB1E672EF5161A6F3F0A7340760" xlink:to="loc_us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_F5D411152B32C70705D9F3F0A734F406" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EquityMethodInvesteeNameDomain" xlink:label="loc_us-gaap_EquityMethodInvesteeNameDomain_38D78C235F4DCDA2199FF3F0A73484F8_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_F5D411152B32C70705D9F3F0A734F406" xlink:to="loc_us-gaap_EquityMethodInvesteeNameDomain_38D78C235F4DCDA2199FF3F0A73484F8_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EquityMethodInvesteeNameDomain" xlink:label="loc_us-gaap_EquityMethodInvesteeNameDomain_38D78C235F4DCDA2199FF3F0A73484F8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_F5D411152B32C70705D9F3F0A734F406" xlink:to="loc_us-gaap_EquityMethodInvesteeNameDomain_38D78C235F4DCDA2199FF3F0A73484F8" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_CrossCountryInfrastructureMember" xlink:label="loc_mtz_CrossCountryInfrastructureMember_270EA545F1798E6099CEF3F0A7343FDF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityMethodInvesteeNameDomain_38D78C235F4DCDA2199FF3F0A73484F8" xlink:to="loc_mtz_CrossCountryInfrastructureMember_270EA545F1798E6099CEF3F0A7343FDF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_BA7D35DC84D4C3678119F3F0A7344C3D" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_2D54CEB1E672EF5161A6F3F0A7340760" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_BA7D35DC84D4C3678119F3F0A7344C3D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_B3C24F307138B84C305BF3F0A7348787_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_BA7D35DC84D4C3678119F3F0A7344C3D" xlink:to="loc_us-gaap_RelatedPartyDomain_B3C24F307138B84C305BF3F0A7348787_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_B3C24F307138B84C305BF3F0A7348787" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_BA7D35DC84D4C3678119F3F0A7344C3D" xlink:to="loc_us-gaap_RelatedPartyDomain_B3C24F307138B84C305BF3F0A7348787" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ImmediateFamilyMemberOfManagementOrPrincipalOwnerMember" xlink:label="loc_us-gaap_ImmediateFamilyMemberOfManagementOrPrincipalOwnerMember_4A8D1675171747DE4ACAF3F0A7353053" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_B3C24F307138B84C305BF3F0A7348787" xlink:to="loc_us-gaap_ImmediateFamilyMemberOfManagementOrPrincipalOwnerMember_4A8D1675171747DE4ACAF3F0A7353053" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionAxis" xlink:label="loc_us-gaap_RelatedPartyTransactionAxis_DF665A5D451DB504F7B1F3F0A73512EC" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_2D54CEB1E672EF5161A6F3F0A7340760" xlink:to="loc_us-gaap_RelatedPartyTransactionAxis_DF665A5D451DB504F7B1F3F0A73512EC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionDomain" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_9CEA1445C5FB143844D3F3F0A735D495_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_DF665A5D451DB504F7B1F3F0A73512EC" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_9CEA1445C5FB143844D3F3F0A735D495_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionDomain" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_9CEA1445C5FB143844D3F3F0A735D495" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_DF665A5D451DB504F7B1F3F0A73512EC" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_9CEA1445C5FB143844D3F3F0A735D495" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_MachineryAndEquipmentMember" xlink:label="loc_us-gaap_MachineryAndEquipmentMember_EC978BE1CF570B396836F3F0A7358467" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionDomain_9CEA1445C5FB143844D3F3F0A735D495" xlink:to="loc_us-gaap_MachineryAndEquipmentMember_EC978BE1CF570B396836F3F0A7358467" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_EquityInvestmentWithoutReadilyDeterminableFairValueOwnershipPercentage" xlink:label="loc_mtz_EquityInvestmentWithoutReadilyDeterminableFairValueOwnershipPercentage_2579E93C8C757A5E4495F3F0A73A80A4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_7C7504F72EF2EEF04C81F3F0A735EB63" xlink:to="loc_mtz_EquityInvestmentWithoutReadilyDeterminableFairValueOwnershipPercentage_2579E93C8C757A5E4495F3F0A73A80A4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionExpensesFromTransactionsWithRelatedParty" xlink:label="loc_us-gaap_RelatedPartyTransactionExpensesFromTransactionsWithRelatedParty_C02CE777F283D03B77B4F3F0A73A3E5E" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_7C7504F72EF2EEF04C81F3F0A735EB63" xlink:to="loc_us-gaap_RelatedPartyTransactionExpensesFromTransactionsWithRelatedParty_C02CE777F283D03B77B4F3F0A73A3E5E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AccountsPayableRelatedPartiesCurrentAndNoncurrent" xlink:label="loc_us-gaap_AccountsPayableRelatedPartiesCurrentAndNoncurrent_1D349B2AEBDCD516E4CAF3F0A73A2958" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_7C7504F72EF2EEF04C81F3F0A735EB63" xlink:to="loc_us-gaap_AccountsPayableRelatedPartiesCurrentAndNoncurrent_1D349B2AEBDCD516E4CAF3F0A73A2958" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.mastec.com/role/RelatedPartyTransactionsContractualJointVentureNarrativeDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionLineItems" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_3EE5601E2BD25E72347B0F2D2309EF47" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_97200500496E689D2DF30F2D2302DF15" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_3EE5601E2BD25E72347B0F2D2309EF47" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_97200500496E689D2DF30F2D2302DF15" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_8299299B1524F0ECD00B0F2D23021C13" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_97200500496E689D2DF30F2D2302DF15" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_8299299B1524F0ECD00B0F2D23021C13" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_5C15C83C26890C5387710F2D230262BF_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_8299299B1524F0ECD00B0F2D23021C13" xlink:to="loc_us-gaap_RelatedPartyDomain_5C15C83C26890C5387710F2D230262BF_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_5C15C83C26890C5387710F2D230262BF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_8299299B1524F0ECD00B0F2D23021C13" xlink:to="loc_us-gaap_RelatedPartyDomain_5C15C83C26890C5387710F2D230262BF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CorporateJointVentureMember" xlink:label="loc_us-gaap_CorporateJointVentureMember_F9173BAFAA2DB5B307FC0F2D23027E5C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_5C15C83C26890C5387710F2D230262BF" xlink:to="loc_us-gaap_CorporateJointVentureMember_F9173BAFAA2DB5B307FC0F2D23027E5C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessAcquisitionAxis" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_B2D1B4A503DA8C92C0B50F2D23028BA0" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_97200500496E689D2DF30F2D2302DF15" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_B2D1B4A503DA8C92C0B50F2D23028BA0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_110EA7E97F855071347A0F2D2303F831_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_B2D1B4A503DA8C92C0B50F2D23028BA0" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_110EA7E97F855071347A0F2D2303F831_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_110EA7E97F855071347A0F2D2303F831" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_B2D1B4A503DA8C92C0B50F2D23028BA0" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_110EA7E97F855071347A0F2D2303F831" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_PacerMember" xlink:label="loc_mtz_PacerMember_E9427FC30AFD142D25250F2D23080559" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_110EA7E97F855071347A0F2D2303F831" xlink:to="loc_mtz_PacerMember_E9427FC30AFD142D25250F2D23080559" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CurrencyAxis" xlink:label="loc_us-gaap_CurrencyAxis_A13D1B49E2493F3954CB0F2D23084716" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_97200500496E689D2DF30F2D2302DF15" xlink:to="loc_us-gaap_CurrencyAxis_A13D1B49E2493F3954CB0F2D23084716" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.sec.gov/currency/2017/currency-2017-01-31.xsd#currency_AllCurrenciesDomain" xlink:label="loc_currency_AllCurrenciesDomain_97E295562D74EF5A28D40F2D2308097D_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CurrencyAxis_A13D1B49E2493F3954CB0F2D23084716" xlink:to="loc_currency_AllCurrenciesDomain_97E295562D74EF5A28D40F2D2308097D_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.sec.gov/currency/2017/currency-2017-01-31.xsd#currency_AllCurrenciesDomain" xlink:label="loc_currency_AllCurrenciesDomain_97E295562D74EF5A28D40F2D2308097D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CurrencyAxis_A13D1B49E2493F3954CB0F2D23084716" xlink:to="loc_currency_AllCurrenciesDomain_97E295562D74EF5A28D40F2D2308097D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.sec.gov/currency/2017/currency-2017-01-31.xsd#currency_CAD" xlink:label="loc_currency_CAD_CB730F8BF88DF12C14670F2D23087554" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_currency_AllCurrenciesDomain_97E295562D74EF5A28D40F2D2308097D" xlink:to="loc_currency_CAD_CB730F8BF88DF12C14670F2D23087554" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_GuaranteeObligationsByNatureAxis" xlink:label="loc_us-gaap_GuaranteeObligationsByNatureAxis_19EC92BD255B646722780F2D2308A514" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_97200500496E689D2DF30F2D2302DF15" xlink:to="loc_us-gaap_GuaranteeObligationsByNatureAxis_19EC92BD255B646722780F2D2308A514" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_GuaranteeObligationsNatureDomain" xlink:label="loc_us-gaap_GuaranteeObligationsNatureDomain_9C3F1C983CF61DED18750F2D23082DA0_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_GuaranteeObligationsByNatureAxis_19EC92BD255B646722780F2D2308A514" xlink:to="loc_us-gaap_GuaranteeObligationsNatureDomain_9C3F1C983CF61DED18750F2D23082DA0_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_GuaranteeObligationsNatureDomain" xlink:label="loc_us-gaap_GuaranteeObligationsNatureDomain_9C3F1C983CF61DED18750F2D23082DA0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_GuaranteeObligationsByNatureAxis_19EC92BD255B646722780F2D2308A514" xlink:to="loc_us-gaap_GuaranteeObligationsNatureDomain_9C3F1C983CF61DED18750F2D23082DA0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PerformanceGuaranteeMember" xlink:label="loc_us-gaap_PerformanceGuaranteeMember_2F899D4E9E22B91532E60F2D2308C449" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GuaranteeObligationsNatureDomain_9C3F1C983CF61DED18750F2D23082DA0" xlink:to="loc_us-gaap_PerformanceGuaranteeMember_2F899D4E9E22B91532E60F2D2308C449" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_OtherCommitmentsAxis" xlink:label="loc_us-gaap_OtherCommitmentsAxis_846E8D0F96ECA04C4D220F2D230887FB" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_97200500496E689D2DF30F2D2302DF15" xlink:to="loc_us-gaap_OtherCommitmentsAxis_846E8D0F96ECA04C4D220F2D230887FB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_OtherCommitmentsDomain" xlink:label="loc_us-gaap_OtherCommitmentsDomain_C79E02F97DCA597EB0D20F2D2309F34F_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_OtherCommitmentsAxis_846E8D0F96ECA04C4D220F2D230887FB" xlink:to="loc_us-gaap_OtherCommitmentsDomain_C79E02F97DCA597EB0D20F2D2309F34F_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_OtherCommitmentsDomain" xlink:label="loc_us-gaap_OtherCommitmentsDomain_C79E02F97DCA597EB0D20F2D2309F34F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_OtherCommitmentsAxis_846E8D0F96ECA04C4D220F2D230887FB" xlink:to="loc_us-gaap_OtherCommitmentsDomain_C79E02F97DCA597EB0D20F2D2309F34F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CapitalSupportAgreementMember" xlink:label="loc_us-gaap_CapitalSupportAgreementMember_05BEBB73FA14BF1B41190F2D23096681" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherCommitmentsDomain_C79E02F97DCA597EB0D20F2D2309F34F" xlink:to="loc_us-gaap_CapitalSupportAgreementMember_05BEBB73FA14BF1B41190F2D23096681" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_ProportionatelyConsolidatedJointVentureOwnershipPercentage" xlink:label="loc_mtz_ProportionatelyConsolidatedJointVentureOwnershipPercentage_4EB0B48E6349AA1B21E20F2D23099CD0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_3EE5601E2BD25E72347B0F2D2309EF47" xlink:to="loc_mtz_ProportionatelyConsolidatedJointVentureOwnershipPercentage_4EB0B48E6349AA1B21E20F2D23099CD0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RevenueFromRelatedParties" xlink:label="loc_us-gaap_RevenueFromRelatedParties_5FBE5709465F80B7F1500F2D2309DBF7" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_3EE5601E2BD25E72347B0F2D2309EF47" xlink:to="loc_us-gaap_RevenueFromRelatedParties_5FBE5709465F80B7F1500F2D2309DBF7" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_AccountsReceivableNetOfBillingsInExcessOfCostsRelatedParties" xlink:label="loc_mtz_AccountsReceivableNetOfBillingsInExcessOfCostsRelatedParties_AA73E4C6B4C784FAC9FE0F2D2309DA68" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_3EE5601E2BD25E72347B0F2D2309EF47" xlink:to="loc_mtz_AccountsReceivableNetOfBillingsInExcessOfCostsRelatedParties_AA73E4C6B4C784FAC9FE0F2D2309DA68" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_GuaranteeObligationsMaximumExposure" xlink:label="loc_us-gaap_GuaranteeObligationsMaximumExposure_1D0158D0D13DC2B785F20F2D230974B9" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_3EE5601E2BD25E72347B0F2D2309EF47" xlink:to="loc_us-gaap_GuaranteeObligationsMaximumExposure_1D0158D0D13DC2B785F20F2D230974B9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PaymentsForAdvanceToAffiliate" xlink:label="loc_us-gaap_PaymentsForAdvanceToAffiliate_24A4C8D710331E3288630F2D23092008" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_3EE5601E2BD25E72347B0F2D2309EF47" xlink:to="loc_us-gaap_PaymentsForAdvanceToAffiliate_24A4C8D710331E3288630F2D23092008" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_OtherCommitment" xlink:label="loc_us-gaap_OtherCommitment_8F55A409F7D02117A99C0F2D2309697D" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_3EE5601E2BD25E72347B0F2D2309EF47" xlink:to="loc_us-gaap_OtherCommitment_8F55A409F7D02117A99C0F2D2309697D" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.mastec.com/role/RelatedPartyTransactionsEquityMethodInvestmentNarrativeDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionLineItems" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_62610946D4848C3BC223178D3AABBD1E" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_9148E0EB7817339AB496178D3AAA07DF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_62610946D4848C3BC223178D3AABBD1E" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_9148E0EB7817339AB496178D3AAA07DF" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_F9C30D52A57A562C2AF3178D3AAA54F8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_9148E0EB7817339AB496178D3AAA07DF" xlink:to="loc_us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_F9C30D52A57A562C2AF3178D3AAA54F8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EquityMethodInvesteeNameDomain" xlink:label="loc_us-gaap_EquityMethodInvesteeNameDomain_B47A57B7EB47CC8F8ECE178D3AAA3F95_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_F9C30D52A57A562C2AF3178D3AAA54F8" xlink:to="loc_us-gaap_EquityMethodInvesteeNameDomain_B47A57B7EB47CC8F8ECE178D3AAA3F95_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EquityMethodInvesteeNameDomain" xlink:label="loc_us-gaap_EquityMethodInvesteeNameDomain_B47A57B7EB47CC8F8ECE178D3AAA3F95" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_F9C30D52A57A562C2AF3178D3AAA54F8" xlink:to="loc_us-gaap_EquityMethodInvesteeNameDomain_B47A57B7EB47CC8F8ECE178D3AAA3F95" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_RelatedPartyInvestmentMember" xlink:label="loc_mtz_RelatedPartyInvestmentMember_45A1D6330F2C26F5482D178D3AAAB808" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityMethodInvesteeNameDomain_B47A57B7EB47CC8F8ECE178D3AAA3F95" xlink:to="loc_mtz_RelatedPartyInvestmentMember_45A1D6330F2C26F5482D178D3AAAB808" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_B2896D3F2F15A705DF84178D3AAA9350" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_9148E0EB7817339AB496178D3AAA07DF" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_B2896D3F2F15A705DF84178D3AAA9350" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_21F9A1FF85D8F1414FA7178D3AABD6B3_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_B2896D3F2F15A705DF84178D3AAA9350" xlink:to="loc_us-gaap_RelatedPartyDomain_21F9A1FF85D8F1414FA7178D3AABD6B3_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_21F9A1FF85D8F1414FA7178D3AABD6B3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_B2896D3F2F15A705DF84178D3AAA9350" xlink:to="loc_us-gaap_RelatedPartyDomain_21F9A1FF85D8F1414FA7178D3AABD6B3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EquityMethodInvesteeMember" xlink:label="loc_us-gaap_EquityMethodInvesteeMember_9EEE94B21121939823CF178D3AABCB33" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_21F9A1FF85D8F1414FA7178D3AABD6B3" xlink:to="loc_us-gaap_EquityMethodInvesteeMember_9EEE94B21121939823CF178D3AABCB33" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EquityMethodInvestmentOwnershipPercentage" xlink:label="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_25E820FD1F1969E2A989178D3AAB22CD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_62610946D4848C3BC223178D3AABBD1E" xlink:to="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_25E820FD1F1969E2A989178D3AAB22CD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DueFromAffiliates" xlink:label="loc_us-gaap_DueFromAffiliates_D0BD0C9B1E5B3B98E448178D3AB0106F" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_62610946D4848C3BC223178D3AABBD1E" xlink:to="loc_us-gaap_DueFromAffiliates_D0BD0C9B1E5B3B98E448178D3AB0106F" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.mastec.com/role/RelatedPartyTransactionsLeasesAndOtherTransactionsNarrativeDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionLineItems" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_F0704490608D6B0DEC4B0F2CF6B12256" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_8CD819C0FFF4F1021B3A0F2CF6AACE12" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_F0704490608D6B0DEC4B0F2CF6B12256" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_8CD819C0FFF4F1021B3A0F2CF6AACE12" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_D060ABBE8C08092FB0C90F2CF6AA78B4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_8CD819C0FFF4F1021B3A0F2CF6AACE12" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_D060ABBE8C08092FB0C90F2CF6AA78B4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_71F929FD8519885A60A50F2CF6AA6BAB_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_D060ABBE8C08092FB0C90F2CF6AA78B4" xlink:to="loc_us-gaap_RelatedPartyDomain_71F929FD8519885A60A50F2CF6AA6BAB_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_71F929FD8519885A60A50F2CF6AA6BAB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_D060ABBE8C08092FB0C90F2CF6AA78B4" xlink:to="loc_us-gaap_RelatedPartyDomain_71F929FD8519885A60A50F2CF6AA6BAB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ManagementMember" xlink:label="loc_us-gaap_ManagementMember_8962C3F50BEE1CF452320F2CF6AA6AC0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_71F929FD8519885A60A50F2CF6AA6BAB" xlink:to="loc_us-gaap_ManagementMember_8962C3F50BEE1CF452320F2CF6AA6AC0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ImmediateFamilyMemberOfManagementOrPrincipalOwnerMember" xlink:label="loc_us-gaap_ImmediateFamilyMemberOfManagementOrPrincipalOwnerMember_9FC2193F6A06874AC72D0F2CF6AF6AB4" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_71F929FD8519885A60A50F2CF6AA6BAB" xlink:to="loc_us-gaap_ImmediateFamilyMemberOfManagementOrPrincipalOwnerMember_9FC2193F6A06874AC72D0F2CF6AF6AB4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionAxis" xlink:label="loc_us-gaap_RelatedPartyTransactionAxis_D0AE5FE42259C21284270F2CF6AF2DD8" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_8CD819C0FFF4F1021B3A0F2CF6AACE12" xlink:to="loc_us-gaap_RelatedPartyTransactionAxis_D0AE5FE42259C21284270F2CF6AF2DD8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionDomain" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_87B495ABCA67FAD622580F2CF6AF0DB2_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_D0AE5FE42259C21284270F2CF6AF2DD8" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_87B495ABCA67FAD622580F2CF6AF0DB2_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionDomain" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_87B495ABCA67FAD622580F2CF6AF0DB2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_D0AE5FE42259C21284270F2CF6AF2DD8" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_87B495ABCA67FAD622580F2CF6AF0DB2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LeaseAgreementsMember" xlink:label="loc_us-gaap_LeaseAgreementsMember_4E1FBD6E253FC6E1ACA30F2CF6B0F794" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionDomain_87B495ABCA67FAD622580F2CF6AF0DB2" xlink:to="loc_us-gaap_LeaseAgreementsMember_4E1FBD6E253FC6E1ACA30F2CF6B0F794" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ServiceAgreementsMember" xlink:label="loc_us-gaap_ServiceAgreementsMember_B17E4DB44D54C0D4887D0F2CF6B0F4C2" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionDomain_87B495ABCA67FAD622580F2CF6AF0DB2" xlink:to="loc_us-gaap_ServiceAgreementsMember_B17E4DB44D54C0D4887D0F2CF6B0F4C2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConstructionContractsMember" xlink:label="loc_us-gaap_ConstructionContractsMember_447DA556A0B10907CD280F2CF6B0B6A8" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionDomain_87B495ABCA67FAD622580F2CF6AF0DB2" xlink:to="loc_us-gaap_ConstructionContractsMember_447DA556A0B10907CD280F2CF6B0B6A8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessAcquisitionAxis" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_A6D3D6FE5895448C4C9C0F2CF6B0D3B8" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_8CD819C0FFF4F1021B3A0F2CF6AACE12" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_A6D3D6FE5895448C4C9C0F2CF6B0D3B8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_A5279F766BBA8E4850FC0F2CF6B0BFCF_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_A6D3D6FE5895448C4C9C0F2CF6B0D3B8" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_A5279F766BBA8E4850FC0F2CF6B0BFCF_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_A5279F766BBA8E4850FC0F2CF6B0BFCF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_A6D3D6FE5895448C4C9C0F2CF6B0D3B8" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_A5279F766BBA8E4850FC0F2CF6B0BFCF" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_OilAndGas2017AcquisitionMember" xlink:label="loc_mtz_OilAndGas2017AcquisitionMember_1FFA2E84F45CD788BBC50F2CF6B04A2A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_A5279F766BBA8E4850FC0F2CF6B0BFCF" xlink:to="loc_mtz_OilAndGas2017AcquisitionMember_1FFA2E84F45CD788BBC50F2CF6B04A2A" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_ConstructionManagementFirmSpecializingInSteelBuildingSystemsMember" xlink:label="loc_mtz_ConstructionManagementFirmSpecializingInSteelBuildingSystemsMember_8FF8C2A058BFF92B097F0F2CF6B03E44" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_A5279F766BBA8E4850FC0F2CF6B0BFCF" xlink:to="loc_mtz_ConstructionManagementFirmSpecializingInSteelBuildingSystemsMember_8FF8C2A058BFF92B097F0F2CF6B03E44" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ContingentConsiderationByTypeAxis" xlink:label="loc_us-gaap_ContingentConsiderationByTypeAxis_B0BD66431DA5FC220EAB0F2CF6B063C6" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_8CD819C0FFF4F1021B3A0F2CF6AACE12" xlink:to="loc_us-gaap_ContingentConsiderationByTypeAxis_B0BD66431DA5FC220EAB0F2CF6B063C6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ContingentConsiderationTypeDomain" xlink:label="loc_us-gaap_ContingentConsiderationTypeDomain_19FF44FC355F852C459D0F2CF6B0497A_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ContingentConsiderationByTypeAxis_B0BD66431DA5FC220EAB0F2CF6B063C6" xlink:to="loc_us-gaap_ContingentConsiderationTypeDomain_19FF44FC355F852C459D0F2CF6B0497A_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ContingentConsiderationTypeDomain" xlink:label="loc_us-gaap_ContingentConsiderationTypeDomain_19FF44FC355F852C459D0F2CF6B0497A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ContingentConsiderationByTypeAxis_B0BD66431DA5FC220EAB0F2CF6B063C6" xlink:to="loc_us-gaap_ContingentConsiderationTypeDomain_19FF44FC355F852C459D0F2CF6B0497A" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_EarnoutArrangementsMember" xlink:label="loc_mtz_EarnoutArrangementsMember_9414E901A821E4DCE1CF0F2CF6B09FE5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ContingentConsiderationTypeDomain_19FF44FC355F852C459D0F2CF6B0497A" xlink:to="loc_mtz_EarnoutArrangementsMember_9414E901A821E4DCE1CF0F2CF6B09FE5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionExpensesFromTransactionsWithRelatedParty" xlink:label="loc_us-gaap_RelatedPartyTransactionExpensesFromTransactionsWithRelatedParty_00301F49FB98A3E8B16D0F2CF6B1284E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_F0704490608D6B0DEC4B0F2CF6B12256" xlink:to="loc_us-gaap_RelatedPartyTransactionExpensesFromTransactionsWithRelatedParty_00301F49FB98A3E8B16D0F2CF6B1284E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AccountsPayableRelatedPartiesCurrentAndNoncurrent" xlink:label="loc_us-gaap_AccountsPayableRelatedPartiesCurrentAndNoncurrent_18F2103AEBF6103EC2010F2CF6B1AFDE" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_F0704490608D6B0DEC4B0F2CF6B12256" xlink:to="loc_us-gaap_AccountsPayableRelatedPartiesCurrentAndNoncurrent_18F2103AEBF6103EC2010F2CF6B1AFDE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RevenueFromRelatedParties" xlink:label="loc_us-gaap_RevenueFromRelatedParties_DC65628F7DFB2165C48D0F2CF6B1E0C5" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_F0704490608D6B0DEC4B0F2CF6B12256" xlink:to="loc_us-gaap_RevenueFromRelatedParties_DC65628F7DFB2165C48D0F2CF6B1E0C5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AccountsReceivableRelatedParties" xlink:label="loc_us-gaap_AccountsReceivableRelatedParties_7326F716A2A7204513F40F2CF6B1AD78" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_F0704490608D6B0DEC4B0F2CF6B12256" xlink:to="loc_us-gaap_AccountsReceivableRelatedParties_7326F716A2A7204513F40F2CF6B1AD78" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PaymentsToAcquireBusinessesGross" xlink:label="loc_us-gaap_PaymentsToAcquireBusinessesGross_8D28A3C75EF71A8A0BB30F2CF6B19A2A" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_F0704490608D6B0DEC4B0F2CF6B12256" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesGross_8D28A3C75EF71A8A0BB30F2CF6B19A2A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessCombinationContingentConsiderationLiability" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationLiability_991A54249A1AB648167C0F2CF6B1A113" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_F0704490608D6B0DEC4B0F2CF6B12256" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationLiability_991A54249A1AB648167C0F2CF6B1A113" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedFinancialLiabilities" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedFinancialLiabilities_B5505356D69C89EEB4FD0F2CF6B13BD7" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_F0704490608D6B0DEC4B0F2CF6B12256" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedFinancialLiabilities_B5505356D69C89EEB4FD0F2CF6B13BD7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RepaymentsOfNotesPayable" xlink:label="loc_us-gaap_RepaymentsOfNotesPayable_3302F2A02D9F9A60DB190F2CF6B1191C" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_F0704490608D6B0DEC4B0F2CF6B12256" xlink:to="loc_us-gaap_RepaymentsOfNotesPayable_3302F2A02D9F9A60DB190F2CF6B1191C" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.mastec.com/role/RelatedPartyTransactionsNonControllingInterestsNarrativeDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionLineItems" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_30F7B2A00FED413CAB2B178D3C4C8917" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_6645A73646A8AA4DE189178D3C4B9CF2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_30F7B2A00FED413CAB2B178D3C4C8917" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_6645A73646A8AA4DE189178D3C4B9CF2" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_E24FE59C1ADCA6ED9244178D3C4B4557" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_6645A73646A8AA4DE189178D3C4B9CF2" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_E24FE59C1ADCA6ED9244178D3C4B4557" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_C05AA48DB4C60B8EE133178D3C4BB0DA_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_E24FE59C1ADCA6ED9244178D3C4B4557" xlink:to="loc_us-gaap_RelatedPartyDomain_C05AA48DB4C60B8EE133178D3C4BB0DA_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_C05AA48DB4C60B8EE133178D3C4BB0DA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_E24FE59C1ADCA6ED9244178D3C4B4557" xlink:to="loc_us-gaap_RelatedPartyDomain_C05AA48DB4C60B8EE133178D3C4BB0DA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ManagementMember" xlink:label="loc_us-gaap_ManagementMember_353BFA32F343685A4EC5178D3C4BA0C8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_C05AA48DB4C60B8EE133178D3C4BB0DA" xlink:to="loc_us-gaap_ManagementMember_353BFA32F343685A4EC5178D3C4BA0C8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionAxis" xlink:label="loc_us-gaap_RelatedPartyTransactionAxis_C2DF3BC6F86B02994B4A178D3C4B18ED" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_6645A73646A8AA4DE189178D3C4B9CF2" xlink:to="loc_us-gaap_RelatedPartyTransactionAxis_C2DF3BC6F86B02994B4A178D3C4B18ED" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionDomain" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_52517D4EF214CAD66588178D3C4BB011_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_C2DF3BC6F86B02994B4A178D3C4B18ED" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_52517D4EF214CAD66588178D3C4BB011_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionDomain" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_52517D4EF214CAD66588178D3C4BB011" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_C2DF3BC6F86B02994B4A178D3C4B18ED" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_52517D4EF214CAD66588178D3C4BB011" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_AcquisitionOfNoncontrollingInterestMember" xlink:label="loc_mtz_AcquisitionOfNoncontrollingInterestMember_7A21F86120C3977A097B178D3C4C1D89" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionDomain_52517D4EF214CAD66588178D3C4BB011" xlink:to="loc_mtz_AcquisitionOfNoncontrollingInterestMember_7A21F86120C3977A097B178D3C4C1D89" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ContingentConsiderationByTypeAxis" xlink:label="loc_us-gaap_ContingentConsiderationByTypeAxis_D6CA650F1FDFB9DA7173178D3C4C20B4" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_6645A73646A8AA4DE189178D3C4B9CF2" xlink:to="loc_us-gaap_ContingentConsiderationByTypeAxis_D6CA650F1FDFB9DA7173178D3C4C20B4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ContingentConsiderationTypeDomain" xlink:label="loc_us-gaap_ContingentConsiderationTypeDomain_32033A1A1C00E3080AC6178D3C4C4543_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ContingentConsiderationByTypeAxis_D6CA650F1FDFB9DA7173178D3C4C20B4" xlink:to="loc_us-gaap_ContingentConsiderationTypeDomain_32033A1A1C00E3080AC6178D3C4C4543_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ContingentConsiderationTypeDomain" xlink:label="loc_us-gaap_ContingentConsiderationTypeDomain_32033A1A1C00E3080AC6178D3C4C4543" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ContingentConsiderationByTypeAxis_D6CA650F1FDFB9DA7173178D3C4C20B4" xlink:to="loc_us-gaap_ContingentConsiderationTypeDomain_32033A1A1C00E3080AC6178D3C4C4543" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_EarnoutArrangementsMember" xlink:label="loc_mtz_EarnoutArrangementsMember_FDA8B301CF6FB05059C1178D3C4CD90C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ContingentConsiderationTypeDomain_32033A1A1C00E3080AC6178D3C4C4543" xlink:to="loc_mtz_EarnoutArrangementsMember_FDA8B301CF6FB05059C1178D3C4CD90C" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_NumberOfSubsidiaries" xlink:label="loc_mtz_NumberOfSubsidiaries_04BB6308F1EE5B481680178D3C4CBFEC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_30F7B2A00FED413CAB2B178D3C4C8917" xlink:to="loc_mtz_NumberOfSubsidiaries_04BB6308F1EE5B481680178D3C4CBFEC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PaymentsToAcquireAdditionalInterestInSubsidiaries" xlink:label="loc_us-gaap_PaymentsToAcquireAdditionalInterestInSubsidiaries_5718934ADA889F323F40178D3C4CD256" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_30F7B2A00FED413CAB2B178D3C4C8917" xlink:to="loc_us-gaap_PaymentsToAcquireAdditionalInterestInSubsidiaries_5718934ADA889F323F40178D3C4CD256" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessCombinationContingentConsiderationLiability" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationLiability_269E755E9D969C0C27F5178D3C4CDF34" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_30F7B2A00FED413CAB2B178D3C4C8917" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationLiability_269E755E9D969C0C27F5178D3C4CDF34" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PaymentsToMinorityShareholders" xlink:label="loc_us-gaap_PaymentsToMinorityShareholders_3800F1042150131D725D178D3C4C9380" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_30F7B2A00FED413CAB2B178D3C4C8917" xlink:to="loc_us-gaap_PaymentsToMinorityShareholders_3800F1042150131D725D178D3C4C9380" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.mastec.com/role/RelatedPartyTransactionsSplitDollarAgreementsNarrativeDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionLineItems" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_763351E5B4A2414AC3FC0351113C0674" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_55FC81AFF55BDC4D44E00351113B6290" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_763351E5B4A2414AC3FC0351113C0674" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_55FC81AFF55BDC4D44E00351113B6290" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_5E69412D179ACE024A580351113BF350" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_55FC81AFF55BDC4D44E00351113B6290" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_5E69412D179ACE024A580351113BF350" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_E9716936DC34A77DE8430351113B5701_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_5E69412D179ACE024A580351113BF350" xlink:to="loc_us-gaap_RelatedPartyDomain_E9716936DC34A77DE8430351113B5701_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_E9716936DC34A77DE8430351113B5701" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_5E69412D179ACE024A580351113BF350" xlink:to="loc_us-gaap_RelatedPartyDomain_E9716936DC34A77DE8430351113B5701" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ChiefExecutiveOfficerMember" xlink:label="loc_us-gaap_ChiefExecutiveOfficerMember_C92278D6E51FEFD192440351113B1686" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_E9716936DC34A77DE8430351113B5701" xlink:to="loc_us-gaap_ChiefExecutiveOfficerMember_C92278D6E51FEFD192440351113B1686" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BoardOfDirectorsChairmanMember" xlink:label="loc_us-gaap_BoardOfDirectorsChairmanMember_7B3CFC3C886FC77F7C350351113B6F51" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_E9716936DC34A77DE8430351113B5701" xlink:to="loc_us-gaap_BoardOfDirectorsChairmanMember_7B3CFC3C886FC77F7C350351113B6F51" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ExecutiveOfficerMember" xlink:label="loc_us-gaap_ExecutiveOfficerMember_33978ED198BAA09FCA230351113C5E0B" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_E9716936DC34A77DE8430351113B5701" xlink:to="loc_us-gaap_ExecutiveOfficerMember_33978ED198BAA09FCA230351113C5E0B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BalanceSheetLocationAxis" xlink:label="loc_us-gaap_BalanceSheetLocationAxis_CCDE8EA526D16D0FEE7C0351113CEE2A" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_55FC81AFF55BDC4D44E00351113B6290" xlink:to="loc_us-gaap_BalanceSheetLocationAxis_CCDE8EA526D16D0FEE7C0351113CEE2A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BalanceSheetLocationDomain" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_E1E1FB782533D1622B2A0351113C541D_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_CCDE8EA526D16D0FEE7C0351113CEE2A" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_E1E1FB782533D1622B2A0351113C541D_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BalanceSheetLocationDomain" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_E1E1FB782533D1622B2A0351113C541D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_CCDE8EA526D16D0FEE7C0351113CEE2A" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_E1E1FB782533D1622B2A0351113C541D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_OtherNoncurrentAssetsMember" xlink:label="loc_us-gaap_OtherNoncurrentAssetsMember_99E3C8688F459D37EB810351113CB28F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_E1E1FB782533D1622B2A0351113C541D" xlink:to="loc_us-gaap_OtherNoncurrentAssetsMember_99E3C8688F459D37EB810351113CB28F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PaymentsToAcquireLifeInsurancePolicies" xlink:label="loc_us-gaap_PaymentsToAcquireLifeInsurancePolicies_D2A8F7DF03D52A19CAC20351113C98ED" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_763351E5B4A2414AC3FC0351113C0674" xlink:to="loc_us-gaap_PaymentsToAcquireLifeInsurancePolicies_D2A8F7DF03D52A19CAC20351113C98ED" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CashSurrenderValueOfLifeInsurance" xlink:label="loc_us-gaap_CashSurrenderValueOfLifeInsurance_4BD72C5568B41E07CF7B0351113CC868" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_763351E5B4A2414AC3FC0351113C0674" xlink:to="loc_us-gaap_CashSurrenderValueOfLifeInsurance_4BD72C5568B41E07CF7B0351113CC868" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.mastec.com/role/RelatedPartyTransactionsSubcontractingArrangementsAndOtherTransactionsNarrativeDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionLineItems" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_7B3041AFA3D28B807D6B1453E4BBE8B8" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_00CB377DD886FFEF7BA71453E4B9D0BB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_7B3041AFA3D28B807D6B1453E4BBE8B8" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_00CB377DD886FFEF7BA71453E4B9D0BB" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_DF755011BB65776AD6EE1453E4B918FE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_00CB377DD886FFEF7BA71453E4B9D0BB" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_DF755011BB65776AD6EE1453E4B918FE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_3958C67C4141C45307F01453E4B9EFE0_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_DF755011BB65776AD6EE1453E4B918FE" xlink:to="loc_us-gaap_RelatedPartyDomain_3958C67C4141C45307F01453E4B9EFE0_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_3958C67C4141C45307F01453E4B9EFE0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_DF755011BB65776AD6EE1453E4B918FE" xlink:to="loc_us-gaap_RelatedPartyDomain_3958C67C4141C45307F01453E4B9EFE0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ManagementMember" xlink:label="loc_us-gaap_ManagementMember_7F7914394EBCFD65697D1453E4B9C22E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_3958C67C4141C45307F01453E4B9EFE0" xlink:to="loc_us-gaap_ManagementMember_7F7914394EBCFD65697D1453E4B9C22E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ExecutiveOfficerMember" xlink:label="loc_us-gaap_ExecutiveOfficerMember_5C2EAA44CD77363240E51453E4B9204A" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_3958C67C4141C45307F01453E4B9EFE0" xlink:to="loc_us-gaap_ExecutiveOfficerMember_5C2EAA44CD77363240E51453E4B9204A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BoardOfDirectorsChairmanMember" xlink:label="loc_us-gaap_BoardOfDirectorsChairmanMember_A9C83E7E0237A1724BC61453E4B976C1" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_3958C67C4141C45307F01453E4B9EFE0" xlink:to="loc_us-gaap_BoardOfDirectorsChairmanMember_A9C83E7E0237A1724BC61453E4B976C1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionAxis" xlink:label="loc_us-gaap_RelatedPartyTransactionAxis_0728C9C0CCE11B5204891453E4B93D74" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_00CB377DD886FFEF7BA71453E4B9D0BB" xlink:to="loc_us-gaap_RelatedPartyTransactionAxis_0728C9C0CCE11B5204891453E4B93D74" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionDomain" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_7412C2988E908ED473581453E4B92C60_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_0728C9C0CCE11B5204891453E4B93D74" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_7412C2988E908ED473581453E4B92C60_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionDomain" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_7412C2988E908ED473581453E4B92C60" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_0728C9C0CCE11B5204891453E4B93D74" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_7412C2988E908ED473581453E4B92C60" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_SubcontractingArrangementsMember" xlink:label="loc_mtz_SubcontractingArrangementsMember_8FC3D57D62E31A1B56A31453E4BA860D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionDomain_7412C2988E908ED473581453E4B92C60" xlink:to="loc_mtz_SubcontractingArrangementsMember_8FC3D57D62E31A1B56A31453E4BA860D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EmploymentContractsMember" xlink:label="loc_us-gaap_EmploymentContractsMember_EC56804F88FD7E3848C31453E4BA90C4" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionDomain_7412C2988E908ED473581453E4B92C60" xlink:to="loc_us-gaap_EmploymentContractsMember_EC56804F88FD7E3848C31453E4BA90C4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ServiceAgreementsMember" xlink:label="loc_us-gaap_ServiceAgreementsMember_E237E95F3410510942751453E4BA361D" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionDomain_7412C2988E908ED473581453E4B92C60" xlink:to="loc_us-gaap_ServiceAgreementsMember_E237E95F3410510942751453E4BA361D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LeaseAgreementsMember" xlink:label="loc_us-gaap_LeaseAgreementsMember_C1E7C45C690DC1F35F051453E4BA65ED" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionDomain_7412C2988E908ED473581453E4B92C60" xlink:to="loc_us-gaap_LeaseAgreementsMember_C1E7C45C690DC1F35F051453E4BA65ED" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedGoodsAndNonemployeeServicesTransactionBySupplierAxis" xlink:label="loc_us-gaap_ShareBasedGoodsAndNonemployeeServicesTransactionBySupplierAxis_14C0295034999063163D1453E4BAA513" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_00CB377DD886FFEF7BA71453E4B9D0BB" xlink:to="loc_us-gaap_ShareBasedGoodsAndNonemployeeServicesTransactionBySupplierAxis_14C0295034999063163D1453E4BAA513" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedGoodsAndNonemployeeServicesTransactionSupplierDomain" xlink:label="loc_us-gaap_ShareBasedGoodsAndNonemployeeServicesTransactionSupplierDomain_5030BB6995AE35BF31581453E4BA3825_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ShareBasedGoodsAndNonemployeeServicesTransactionBySupplierAxis_14C0295034999063163D1453E4BAA513" xlink:to="loc_us-gaap_ShareBasedGoodsAndNonemployeeServicesTransactionSupplierDomain_5030BB6995AE35BF31581453E4BA3825_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedGoodsAndNonemployeeServicesTransactionSupplierDomain" xlink:label="loc_us-gaap_ShareBasedGoodsAndNonemployeeServicesTransactionSupplierDomain_5030BB6995AE35BF31581453E4BA3825" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ShareBasedGoodsAndNonemployeeServicesTransactionBySupplierAxis_14C0295034999063163D1453E4BAA513" xlink:to="loc_us-gaap_ShareBasedGoodsAndNonemployeeServicesTransactionSupplierDomain_5030BB6995AE35BF31581453E4BA3825" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_RelatedContractorOrSupplierMember" xlink:label="loc_mtz_RelatedContractorOrSupplierMember_F738968CFE53FA9D779F1453E4BA255E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedGoodsAndNonemployeeServicesTransactionSupplierDomain_5030BB6995AE35BF31581453E4BA3825" xlink:to="loc_mtz_RelatedContractorOrSupplierMember_F738968CFE53FA9D779F1453E4BA255E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_MajorCustomersAxis" xlink:label="loc_us-gaap_MajorCustomersAxis_ECB44C7A1EA9F6E216571453E4BADAE9" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_00CB377DD886FFEF7BA71453E4B9D0BB" xlink:to="loc_us-gaap_MajorCustomersAxis_ECB44C7A1EA9F6E216571453E4BADAE9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NameOfMajorCustomerDomain" xlink:label="loc_us-gaap_NameOfMajorCustomerDomain_F588FD16E39C3AD2F7CC1453E4BA96CC_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_MajorCustomersAxis_ECB44C7A1EA9F6E216571453E4BADAE9" xlink:to="loc_us-gaap_NameOfMajorCustomerDomain_F588FD16E39C3AD2F7CC1453E4BA96CC_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NameOfMajorCustomerDomain" xlink:label="loc_us-gaap_NameOfMajorCustomerDomain_F588FD16E39C3AD2F7CC1453E4BA96CC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_MajorCustomersAxis_ECB44C7A1EA9F6E216571453E4BADAE9" xlink:to="loc_us-gaap_NameOfMajorCustomerDomain_F588FD16E39C3AD2F7CC1453E4BA96CC" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_RelatedCustomerMember" xlink:label="loc_mtz_RelatedCustomerMember_8809E313D166486D54571453E4BAF117" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NameOfMajorCustomerDomain_F588FD16E39C3AD2F7CC1453E4BA96CC" xlink:to="loc_mtz_RelatedCustomerMember_8809E313D166486D54571453E4BAF117" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LeaseArrangementTypeAxis" xlink:label="loc_us-gaap_LeaseArrangementTypeAxis_EE93CF2C97931CAC2D431453E4BA365B" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_00CB377DD886FFEF7BA71453E4B9D0BB" xlink:to="loc_us-gaap_LeaseArrangementTypeAxis_EE93CF2C97931CAC2D431453E4BA365B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LeaseArrangementTypeDomain" xlink:label="loc_us-gaap_LeaseArrangementTypeDomain_51159F1ED8C302A03B681453E4BAC1DA_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LeaseArrangementTypeAxis_EE93CF2C97931CAC2D431453E4BA365B" xlink:to="loc_us-gaap_LeaseArrangementTypeDomain_51159F1ED8C302A03B681453E4BAC1DA_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LeaseArrangementTypeDomain" xlink:label="loc_us-gaap_LeaseArrangementTypeDomain_51159F1ED8C302A03B681453E4BAC1DA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LeaseArrangementTypeAxis_EE93CF2C97931CAC2D431453E4BA365B" xlink:to="loc_us-gaap_LeaseArrangementTypeDomain_51159F1ED8C302A03B681453E4BAC1DA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AirTransportationEquipmentMember" xlink:label="loc_us-gaap_AirTransportationEquipmentMember_0647345123D588EBE3E51453E4BB49F5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LeaseArrangementTypeDomain_51159F1ED8C302A03B681453E4BAC1DA" xlink:to="loc_us-gaap_AirTransportationEquipmentMember_0647345123D588EBE3E51453E4BB49F5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.sec.gov/dei/2014/dei-2014-01-31.xsd#dei_EntityNumberOfEmployees" xlink:label="loc_dei_EntityNumberOfEmployees_228BFC979C397436D5EE1453E4BB6EEA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_7B3041AFA3D28B807D6B1453E4BBE8B8" xlink:to="loc_dei_EntityNumberOfEmployees_228BFC979C397436D5EE1453E4BB6EEA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionExpensesFromTransactionsWithRelatedParty" xlink:label="loc_us-gaap_RelatedPartyTransactionExpensesFromTransactionsWithRelatedParty_62FE3923387D5085E4911453E4BB9571" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_7B3041AFA3D28B807D6B1453E4BBE8B8" xlink:to="loc_us-gaap_RelatedPartyTransactionExpensesFromTransactionsWithRelatedParty_62FE3923387D5085E4911453E4BB9571" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AccountsPayableRelatedPartiesCurrentAndNoncurrent" xlink:label="loc_us-gaap_AccountsPayableRelatedPartiesCurrentAndNoncurrent_526ACEAE25ECE3D0FBE11453E4BBA7EC" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_7B3041AFA3D28B807D6B1453E4BBE8B8" xlink:to="loc_us-gaap_AccountsPayableRelatedPartiesCurrentAndNoncurrent_526ACEAE25ECE3D0FBE11453E4BBA7EC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionOtherRevenuesFromTransactionsWithRelatedParty" xlink:label="loc_us-gaap_RelatedPartyTransactionOtherRevenuesFromTransactionsWithRelatedParty_64FE3D167638943FD6171453E4BBD341" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_7B3041AFA3D28B807D6B1453E4BBE8B8" xlink:to="loc_us-gaap_RelatedPartyTransactionOtherRevenuesFromTransactionsWithRelatedParty_64FE3D167638943FD6171453E4BBD341" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DueFromRelatedParties" xlink:label="loc_us-gaap_DueFromRelatedParties_D84A2913ED2BFCC58F751453E4BB1562" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_7B3041AFA3D28B807D6B1453E4BBE8B8" xlink:to="loc_us-gaap_DueFromRelatedParties_D84A2913ED2BFCC58F751453E4BB1562" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RevenueFromRelatedParties" xlink:label="loc_us-gaap_RevenueFromRelatedParties_BEB22094B16EB1D2B6E51453E4BB4C50" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_7B3041AFA3D28B807D6B1453E4BBE8B8" xlink:to="loc_us-gaap_RevenueFromRelatedParties_BEB22094B16EB1D2B6E51453E4BB4C50" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AccountsReceivableRelatedParties" xlink:label="loc_us-gaap_AccountsReceivableRelatedParties_7558BF0B52321CBCEACA1453E4BB2428" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_7B3041AFA3D28B807D6B1453E4BBE8B8" xlink:to="loc_us-gaap_AccountsReceivableRelatedParties_7558BF0B52321CBCEACA1453E4BB2428" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.mastec.com/role/SegmentsAndRelatedInformation" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.mastec.com/role/SegmentsAndRelatedInformationForeignOperationsNarrativeDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SegmentReportingInformationLineItems" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_AF39A92063727FCF91BB029063DDA5CB" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_F5B9418F13E63BA291B2029063D7911C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_AF39A92063727FCF91BB029063DDA5CB" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_F5B9418F13E63BA291B2029063D7911C" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_StatementGeographicalAxis" xlink:label="loc_us-gaap_StatementGeographicalAxis_A76DC27E09B8ECE2FDB0029063D7A58D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_F5B9418F13E63BA291B2029063D7911C" xlink:to="loc_us-gaap_StatementGeographicalAxis_A76DC27E09B8ECE2FDB0029063D7A58D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SegmentGeographicalDomain" xlink:label="loc_us-gaap_SegmentGeographicalDomain_59F2F18B00460B01413D029063D7057F_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementGeographicalAxis_A76DC27E09B8ECE2FDB0029063D7A58D" xlink:to="loc_us-gaap_SegmentGeographicalDomain_59F2F18B00460B01413D029063D7057F_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SegmentGeographicalDomain" xlink:label="loc_us-gaap_SegmentGeographicalDomain_59F2F18B00460B01413D029063D7057F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementGeographicalAxis_A76DC27E09B8ECE2FDB0029063D7A58D" xlink:to="loc_us-gaap_SegmentGeographicalDomain_59F2F18B00460B01413D029063D7057F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.sec.gov/country/2017/country-2017-01-31.xsd#country_US" xlink:label="loc_country_US_5C8ED1F6113BEAACDFE9029063D7B4C5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentGeographicalDomain_59F2F18B00460B01413D029063D7057F" xlink:to="loc_country_US_5C8ED1F6113BEAACDFE9029063D7B4C5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NonUsMember" xlink:label="loc_us-gaap_NonUsMember_93E44856490D26C5B194029063DC41BE" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentGeographicalDomain_59F2F18B00460B01413D029063D7057F" xlink:to="loc_us-gaap_NonUsMember_93E44856490D26C5B194029063DC41BE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConcentrationRiskByBenchmarkAxis" xlink:label="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_DDB7BABAA823CC7FCF7E029063DC445A" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_F5B9418F13E63BA291B2029063D7911C" xlink:to="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_DDB7BABAA823CC7FCF7E029063DC445A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConcentrationRiskBenchmarkDomain" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_E39CFCC27FA464B57FB2029063DC1E6E_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_DDB7BABAA823CC7FCF7E029063DC445A" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_E39CFCC27FA464B57FB2029063DC1E6E_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConcentrationRiskBenchmarkDomain" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_E39CFCC27FA464B57FB2029063DC1E6E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_DDB7BABAA823CC7FCF7E029063DC445A" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_E39CFCC27FA464B57FB2029063DC1E6E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AccountsReceivableMember" xlink:label="loc_us-gaap_AccountsReceivableMember_B29DD1E133A0FBBAA645029063DCE178" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_E39CFCC27FA464B57FB2029063DC1E6E" xlink:to="loc_us-gaap_AccountsReceivableMember_B29DD1E133A0FBBAA645029063DCE178" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConcentrationRiskByTypeAxis" xlink:label="loc_us-gaap_ConcentrationRiskByTypeAxis_2A30C6B66961667D16F9029063DC57F6" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_F5B9418F13E63BA291B2029063D7911C" xlink:to="loc_us-gaap_ConcentrationRiskByTypeAxis_2A30C6B66961667D16F9029063DC57F6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConcentrationRiskTypeDomain" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_DA55F975DB500BD25D4E029063DDD171_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_2A30C6B66961667D16F9029063DC57F6" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_DA55F975DB500BD25D4E029063DDD171_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConcentrationRiskTypeDomain" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_DA55F975DB500BD25D4E029063DDD171" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_2A30C6B66961667D16F9029063DC57F6" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_DA55F975DB500BD25D4E029063DDD171" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_GeographicConcentrationRiskMember" xlink:label="loc_us-gaap_GeographicConcentrationRiskMember_029023F9648791E1F74E029063DD5386" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_DA55F975DB500BD25D4E029063DDD171" xlink:to="loc_us-gaap_GeographicConcentrationRiskMember_029023F9648791E1F74E029063DD5386" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_MajorCustomersAxis" xlink:label="loc_us-gaap_MajorCustomersAxis_F3915F76D1648A5D289C029063DD45FD" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_F5B9418F13E63BA291B2029063D7911C" xlink:to="loc_us-gaap_MajorCustomersAxis_F3915F76D1648A5D289C029063DD45FD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NameOfMajorCustomerDomain" xlink:label="loc_us-gaap_NameOfMajorCustomerDomain_EE77CC4D8804A6930393029063DD4E63_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_MajorCustomersAxis_F3915F76D1648A5D289C029063DD45FD" xlink:to="loc_us-gaap_NameOfMajorCustomerDomain_EE77CC4D8804A6930393029063DD4E63_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NameOfMajorCustomerDomain" xlink:label="loc_us-gaap_NameOfMajorCustomerDomain_EE77CC4D8804A6930393029063DD4E63" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_MajorCustomersAxis_F3915F76D1648A5D289C029063DD45FD" xlink:to="loc_us-gaap_NameOfMajorCustomerDomain_EE77CC4D8804A6930393029063DD4E63" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_ForeignCustomersMember" xlink:label="loc_mtz_ForeignCustomersMember_C7C1DA885671D1FBBE1F029063DDF9F9" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NameOfMajorCustomerDomain_EE77CC4D8804A6930393029063DD4E63" xlink:to="loc_mtz_ForeignCustomersMember_C7C1DA885671D1FBBE1F029063DDF9F9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_Revenues" xlink:label="loc_us-gaap_Revenues_78165D952DF94A0356B3029063DD4192" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_AF39A92063727FCF91BB029063DDA5CB" xlink:to="loc_us-gaap_Revenues_78165D952DF94A0356B3029063DD4192" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PropertyPlantAndEquipmentNet" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_7198957FE46A1493C9EB029063DDB773" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_AF39A92063727FCF91BB029063DDA5CB" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_7198957FE46A1493C9EB029063DDB773" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IntangibleAssetsNetIncludingGoodwill" xlink:label="loc_us-gaap_IntangibleAssetsNetIncludingGoodwill_C0F58E43BDB54CFB4142029063DD87A6" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_AF39A92063727FCF91BB029063DDA5CB" xlink:to="loc_us-gaap_IntangibleAssetsNetIncludingGoodwill_C0F58E43BDB54CFB4142029063DD87A6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConcentrationRiskPercentage1" xlink:label="loc_us-gaap_ConcentrationRiskPercentage1_CC11A4DA22DF2631BBA7029063DD18B8" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_AF39A92063727FCF91BB029063DDA5CB" xlink:to="loc_us-gaap_ConcentrationRiskPercentage1_CC11A4DA22DF2631BBA7029063DD18B8" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.mastec.com/role/SegmentsAndRelatedInformationNarrativeDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SegmentReportingInformationLineItems" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_CA6675E0173A29440B2D121E7076627A" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_70423E25DC408DB34415121E70757376" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_CA6675E0173A29440B2D121E7076627A" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_70423E25DC408DB34415121E70757376" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_StatementBusinessSegmentsAxis" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_B4AAFEEFC08A1D093ABC121E7075DD78" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_70423E25DC408DB34415121E70757376" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_B4AAFEEFC08A1D093ABC121E7075DD78" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SegmentDomain" xlink:label="loc_us-gaap_SegmentDomain_854F160A9781711A4295121E7075B85B_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_B4AAFEEFC08A1D093ABC121E7075DD78" xlink:to="loc_us-gaap_SegmentDomain_854F160A9781711A4295121E7075B85B_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SegmentDomain" xlink:label="loc_us-gaap_SegmentDomain_854F160A9781711A4295121E7075B85B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_B4AAFEEFC08A1D093ABC121E7075DD78" xlink:to="loc_us-gaap_SegmentDomain_854F160A9781711A4295121E7075B85B" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_CommunicationsMember" xlink:label="loc_mtz_CommunicationsMember_D0D4F9189F71AC81A566121E7075A9E3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_854F160A9781711A4295121E7075B85B" xlink:to="loc_mtz_CommunicationsMember_D0D4F9189F71AC81A566121E7075A9E3" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_OilAndGasMember" xlink:label="loc_mtz_OilAndGasMember_C755976304A028039C29121E7075ABCF" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_854F160A9781711A4295121E7075B85B" xlink:to="loc_mtz_OilAndGasMember_C755976304A028039C29121E7075ABCF" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_ElectricalTransmissionMember" xlink:label="loc_mtz_ElectricalTransmissionMember_732CB3EE838087C92635121E707561BB" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_854F160A9781711A4295121E7075B85B" xlink:to="loc_mtz_ElectricalTransmissionMember_732CB3EE838087C92635121E707561BB" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_PowerGenerationAndIndustrialMember" xlink:label="loc_mtz_PowerGenerationAndIndustrialMember_DB3753F6E0CC114B3F96121E70759F34" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_854F160A9781711A4295121E7075B85B" xlink:to="loc_mtz_PowerGenerationAndIndustrialMember_DB3753F6E0CC114B3F96121E70759F34" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_PrimarySegmentsMember" xlink:label="loc_mtz_PrimarySegmentsMember_E59ED7E4C6F337F0E1F6121E707595A2" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_854F160A9781711A4295121E7075B85B" xlink:to="loc_mtz_PrimarySegmentsMember_E59ED7E4C6F337F0E1F6121E707595A2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FactorsUsedToIdentifyEntitysReportableSegments" xlink:label="loc_us-gaap_FactorsUsedToIdentifyEntitysReportableSegments_0B2E3F32E2CADC71CB83121E70769A2D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_CA6675E0173A29440B2D121E7076627A" xlink:to="loc_us-gaap_FactorsUsedToIdentifyEntitysReportableSegments_0B2E3F32E2CADC71CB83121E70769A2D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NumberOfOperatingSegments" xlink:label="loc_us-gaap_NumberOfOperatingSegments_C8C9C715EC0C20AD6A09121E7076DDD5" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_CA6675E0173A29440B2D121E7076627A" xlink:to="loc_us-gaap_NumberOfOperatingSegments_C8C9C715EC0C20AD6A09121E7076DDD5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NumberOfReportableSegments" xlink:label="loc_us-gaap_NumberOfReportableSegments_C23300DDD037CA2DCEFC121E707681D5" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_CA6675E0173A29440B2D121E7076627A" xlink:to="loc_us-gaap_NumberOfReportableSegments_C23300DDD037CA2DCEFC121E707681D5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DescriptionOfTypesOfProductsAndServicesFromWhichEachReportableSegmentDerivesItsRevenues" xlink:label="loc_us-gaap_DescriptionOfTypesOfProductsAndServicesFromWhichEachReportableSegmentDerivesItsRevenues_2C197B5DCFFCECD82E3C121E707698A3" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_CA6675E0173A29440B2D121E7076627A" xlink:to="loc_us-gaap_DescriptionOfTypesOfProductsAndServicesFromWhichEachReportableSegmentDerivesItsRevenues_2C197B5DCFFCECD82E3C121E707698A3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SegmentReportingDescriptionOfAllOtherSegments" xlink:label="loc_us-gaap_SegmentReportingDescriptionOfAllOtherSegments_75F2E827EB382C4DEE0F121E7076CCBE" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_CA6675E0173A29440B2D121E7076627A" xlink:to="loc_us-gaap_SegmentReportingDescriptionOfAllOtherSegments_75F2E827EB382C4DEE0F121E7076CCBE" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.mastec.com/role/SegmentsAndRelatedInformationReconciliationOfConsolidatedIncomeBeforeIncomeTaxesToEbitdaDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.mastec.com/role/SegmentsAndRelatedInformationScheduleOfFinancialInformationByReportableSegmentDepreciationAndAmortizationDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SegmentReportingInformationLineItems" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_17D465EAE17654FBA785B663A33633BF" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_F68B6AFE939B540EB29C22917FACB7A9" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_17D465EAE17654FBA785B663A33633BF" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_F68B6AFE939B540EB29C22917FACB7A9" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConsolidationItemsAxis" xlink:label="loc_us-gaap_ConsolidationItemsAxis_4B7138439A195A7CA2BFE0D752040036" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_F68B6AFE939B540EB29C22917FACB7A9" xlink:to="loc_us-gaap_ConsolidationItemsAxis_4B7138439A195A7CA2BFE0D752040036" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConsolidationItemsDomain" xlink:label="loc_us-gaap_ConsolidationItemsDomain_69C70B883933165C2EB305C9BBF5A20C_8FF700ECD19F568F86EB052BB273C9DB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConsolidationItemsAxis_4B7138439A195A7CA2BFE0D752040036" xlink:to="loc_us-gaap_ConsolidationItemsDomain_69C70B883933165C2EB305C9BBF5A20C_8FF700ECD19F568F86EB052BB273C9DB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConsolidationItemsDomain" xlink:label="loc_us-gaap_ConsolidationItemsDomain_E8F65F5ED5BF5AE1B0CA25E86A442DFB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConsolidationItemsAxis_4B7138439A195A7CA2BFE0D752040036" xlink:to="loc_us-gaap_ConsolidationItemsDomain_E8F65F5ED5BF5AE1B0CA25E86A442DFB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_OperatingSegmentsMember" xlink:label="loc_us-gaap_OperatingSegmentsMember_4C2DF40ED09E50AAB9C31946AC50B689" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConsolidationItemsDomain_E8F65F5ED5BF5AE1B0CA25E86A442DFB" xlink:to="loc_us-gaap_OperatingSegmentsMember_4C2DF40ED09E50AAB9C31946AC50B689" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CorporateNonSegmentMember" xlink:label="loc_us-gaap_CorporateNonSegmentMember_E1628CB5C08D5644B5A937F2E0B7076E" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConsolidationItemsDomain_E8F65F5ED5BF5AE1B0CA25E86A442DFB" xlink:to="loc_us-gaap_CorporateNonSegmentMember_E1628CB5C08D5644B5A937F2E0B7076E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_StatementBusinessSegmentsAxis" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_6CAB285296EA5A13AB40CE39817080E5" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_F68B6AFE939B540EB29C22917FACB7A9" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_6CAB285296EA5A13AB40CE39817080E5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SegmentDomain" xlink:label="loc_us-gaap_SegmentDomain_A3B8332C44167DE566A705C9BBF5FE66_8FF700ECD19F568F86EB052BB273C9DB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_6CAB285296EA5A13AB40CE39817080E5" xlink:to="loc_us-gaap_SegmentDomain_A3B8332C44167DE566A705C9BBF5FE66_8FF700ECD19F568F86EB052BB273C9DB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SegmentDomain" xlink:label="loc_us-gaap_SegmentDomain_2687790A2D755D13BB9C14535F70223B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_6CAB285296EA5A13AB40CE39817080E5" xlink:to="loc_us-gaap_SegmentDomain_2687790A2D755D13BB9C14535F70223B" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_CommunicationsMember" xlink:label="loc_mtz_CommunicationsMember_20E47BA1C78B510A8CF735F9C9A7718A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_2687790A2D755D13BB9C14535F70223B" xlink:to="loc_mtz_CommunicationsMember_20E47BA1C78B510A8CF735F9C9A7718A" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_OilAndGasMember" xlink:label="loc_mtz_OilAndGasMember_C1ABCD2F41E35A67A977F017EB747C0F" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_2687790A2D755D13BB9C14535F70223B" xlink:to="loc_mtz_OilAndGasMember_C1ABCD2F41E35A67A977F017EB747C0F" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_ElectricalTransmissionMember" xlink:label="loc_mtz_ElectricalTransmissionMember_753A355CA0FC5152A294107766622D00" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_2687790A2D755D13BB9C14535F70223B" xlink:to="loc_mtz_ElectricalTransmissionMember_753A355CA0FC5152A294107766622D00" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_PowerGenerationAndIndustrialMember" xlink:label="loc_mtz_PowerGenerationAndIndustrialMember_55B6F6BDADE5573D9E830102D738C4BB" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_2687790A2D755D13BB9C14535F70223B" xlink:to="loc_mtz_PowerGenerationAndIndustrialMember_55B6F6BDADE5573D9E830102D738C4BB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AllOtherSegmentsMember" xlink:label="loc_us-gaap_AllOtherSegmentsMember_68B50B95DC2E563B9801739541CCD50A" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_2687790A2D755D13BB9C14535F70223B" xlink:to="loc_us-gaap_AllOtherSegmentsMember_68B50B95DC2E563B9801739541CCD50A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DepreciationAndAmortizationAbstract" xlink:label="loc_us-gaap_DepreciationAndAmortizationAbstract_21132B8486DE565289E96937D5EDBBFE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_17D465EAE17654FBA785B663A33633BF" xlink:to="loc_us-gaap_DepreciationAndAmortizationAbstract_21132B8486DE565289E96937D5EDBBFE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DepreciationDepletionAndAmortization" xlink:label="loc_us-gaap_DepreciationDepletionAndAmortization_602DFC93EF785C75A530941DAE603190" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DepreciationAndAmortizationAbstract_21132B8486DE565289E96937D5EDBBFE" xlink:to="loc_us-gaap_DepreciationDepletionAndAmortization_602DFC93EF785C75A530941DAE603190" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.mastec.com/role/SegmentsAndRelatedInformationScheduleOfFinancialInformationByReportableSegmentEbitdaDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SegmentReportingInformationLineItems" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_723D3F135F0A5869AEA1C9460339972C" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_F0D402325BB55D3E99378672E1296F4D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_723D3F135F0A5869AEA1C9460339972C" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_F0D402325BB55D3E99378672E1296F4D" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConsolidationItemsAxis" xlink:label="loc_us-gaap_ConsolidationItemsAxis_8B24AA3029C85838ACC1D693AFE913D4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_F0D402325BB55D3E99378672E1296F4D" xlink:to="loc_us-gaap_ConsolidationItemsAxis_8B24AA3029C85838ACC1D693AFE913D4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConsolidationItemsDomain" xlink:label="loc_us-gaap_ConsolidationItemsDomain_5099B8598E03EE05484B05C9BF039FBC_8FF700ECD19F568F86EB052BB273C9DB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConsolidationItemsAxis_8B24AA3029C85838ACC1D693AFE913D4" xlink:to="loc_us-gaap_ConsolidationItemsDomain_5099B8598E03EE05484B05C9BF039FBC_8FF700ECD19F568F86EB052BB273C9DB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConsolidationItemsDomain" xlink:label="loc_us-gaap_ConsolidationItemsDomain_2505C4EFA14057FC82E28A687961B50D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConsolidationItemsAxis_8B24AA3029C85838ACC1D693AFE913D4" xlink:to="loc_us-gaap_ConsolidationItemsDomain_2505C4EFA14057FC82E28A687961B50D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_OperatingSegmentsMember" xlink:label="loc_us-gaap_OperatingSegmentsMember_4C0E60A58A465F17B8F79CF4D3BD1B72" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConsolidationItemsDomain_2505C4EFA14057FC82E28A687961B50D" xlink:to="loc_us-gaap_OperatingSegmentsMember_4C0E60A58A465F17B8F79CF4D3BD1B72" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CorporateNonSegmentMember" xlink:label="loc_us-gaap_CorporateNonSegmentMember_43B415FD58665327A68A4D23DF34A67D" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConsolidationItemsDomain_2505C4EFA14057FC82E28A687961B50D" xlink:to="loc_us-gaap_CorporateNonSegmentMember_43B415FD58665327A68A4D23DF34A67D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_StatementBusinessSegmentsAxis" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_01C70AB4C8FA5B4D8DA54760369979D8" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_F0D402325BB55D3E99378672E1296F4D" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_01C70AB4C8FA5B4D8DA54760369979D8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SegmentDomain" xlink:label="loc_us-gaap_SegmentDomain_07EE9DF2CC4F73B2EF6D05C9BF0374F7_8FF700ECD19F568F86EB052BB273C9DB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_01C70AB4C8FA5B4D8DA54760369979D8" xlink:to="loc_us-gaap_SegmentDomain_07EE9DF2CC4F73B2EF6D05C9BF0374F7_8FF700ECD19F568F86EB052BB273C9DB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SegmentDomain" xlink:label="loc_us-gaap_SegmentDomain_8F068D9E9FFB57379E8A494229DD3E21" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_01C70AB4C8FA5B4D8DA54760369979D8" xlink:to="loc_us-gaap_SegmentDomain_8F068D9E9FFB57379E8A494229DD3E21" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_CommunicationsMember" xlink:label="loc_mtz_CommunicationsMember_CE3591653F2555F0ADE02CFAE9F5B87E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_8F068D9E9FFB57379E8A494229DD3E21" xlink:to="loc_mtz_CommunicationsMember_CE3591653F2555F0ADE02CFAE9F5B87E" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_OilAndGasMember" xlink:label="loc_mtz_OilAndGasMember_572BBCCB73875B7EAC430E519595D6DA" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_8F068D9E9FFB57379E8A494229DD3E21" xlink:to="loc_mtz_OilAndGasMember_572BBCCB73875B7EAC430E519595D6DA" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_ElectricalTransmissionMember" xlink:label="loc_mtz_ElectricalTransmissionMember_62C35E3D982B50EA93FB8F182B0D7F7C" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_8F068D9E9FFB57379E8A494229DD3E21" xlink:to="loc_mtz_ElectricalTransmissionMember_62C35E3D982B50EA93FB8F182B0D7F7C" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_PowerGenerationAndIndustrialMember" xlink:label="loc_mtz_PowerGenerationAndIndustrialMember_03A057F477385214BB3FDC28320330E2" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_8F068D9E9FFB57379E8A494229DD3E21" xlink:to="loc_mtz_PowerGenerationAndIndustrialMember_03A057F477385214BB3FDC28320330E2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AllOtherSegmentsMember" xlink:label="loc_us-gaap_AllOtherSegmentsMember_A0EF9D7DDF2857D9A886E737C6505E12" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_8F068D9E9FFB57379E8A494229DD3E21" xlink:to="loc_us-gaap_AllOtherSegmentsMember_A0EF9D7DDF2857D9A886E737C6505E12" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SegmentReportingInformationIncomeLossBeforeIncomeTaxesAbstract" xlink:label="loc_us-gaap_SegmentReportingInformationIncomeLossBeforeIncomeTaxesAbstract_EA47F377704E556F8649DD4869755FAD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_723D3F135F0A5869AEA1C9460339972C" xlink:to="loc_us-gaap_SegmentReportingInformationIncomeLossBeforeIncomeTaxesAbstract_EA47F377704E556F8649DD4869755FAD" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_Ebitda" xlink:label="loc_mtz_Ebitda_99DC57B5782D5B2EAC5B19619F8C32A9" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationIncomeLossBeforeIncomeTaxesAbstract_EA47F377704E556F8649DD4869755FAD" xlink:to="loc_mtz_Ebitda_99DC57B5782D5B2EAC5B19619F8C32A9" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.mastec.com/role/SegmentsAndRelatedInformationScheduleOfFinancialInformationByReportableSegmentRevenueDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SegmentReportingInformationLineItems" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_75E8CF7310C351A8A9D2DFAE3C66CEDD" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_4538938C868459B8BF7F6398D04EE6CD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_75E8CF7310C351A8A9D2DFAE3C66CEDD" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_4538938C868459B8BF7F6398D04EE6CD" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConsolidationItemsAxis" xlink:label="loc_us-gaap_ConsolidationItemsAxis_A900325EED0F5424BC623AEF3C0ECA83" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_4538938C868459B8BF7F6398D04EE6CD" xlink:to="loc_us-gaap_ConsolidationItemsAxis_A900325EED0F5424BC623AEF3C0ECA83" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConsolidationItemsDomain" xlink:label="loc_us-gaap_ConsolidationItemsDomain_F5E8822554872FA4FA2805C9BC55FED1_8FF700ECD19F568F86EB052BB273C9DB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConsolidationItemsAxis_A900325EED0F5424BC623AEF3C0ECA83" xlink:to="loc_us-gaap_ConsolidationItemsDomain_F5E8822554872FA4FA2805C9BC55FED1_8FF700ECD19F568F86EB052BB273C9DB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConsolidationItemsDomain" xlink:label="loc_us-gaap_ConsolidationItemsDomain_CB88B561DA3655168D28C2E899747801" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConsolidationItemsAxis_A900325EED0F5424BC623AEF3C0ECA83" xlink:to="loc_us-gaap_ConsolidationItemsDomain_CB88B561DA3655168D28C2E899747801" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_OperatingSegmentsMember" xlink:label="loc_us-gaap_OperatingSegmentsMember_D30D2820393553FC9D3CECE958847089" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConsolidationItemsDomain_CB88B561DA3655168D28C2E899747801" xlink:to="loc_us-gaap_OperatingSegmentsMember_D30D2820393553FC9D3CECE958847089" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IntersegmentEliminationMember" xlink:label="loc_us-gaap_IntersegmentEliminationMember_242F1766CCB655F2BB82A8C092936636" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConsolidationItemsDomain_CB88B561DA3655168D28C2E899747801" xlink:to="loc_us-gaap_IntersegmentEliminationMember_242F1766CCB655F2BB82A8C092936636" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_StatementBusinessSegmentsAxis" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_46B6597258D351C3882B2BEF277B4F19" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_4538938C868459B8BF7F6398D04EE6CD" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_46B6597258D351C3882B2BEF277B4F19" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SegmentDomain" xlink:label="loc_us-gaap_SegmentDomain_3E050361CA13758AF48A05C9BC56EFF4_8FF700ECD19F568F86EB052BB273C9DB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_46B6597258D351C3882B2BEF277B4F19" xlink:to="loc_us-gaap_SegmentDomain_3E050361CA13758AF48A05C9BC56EFF4_8FF700ECD19F568F86EB052BB273C9DB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SegmentDomain" xlink:label="loc_us-gaap_SegmentDomain_5C17E281BD0050C8B58E6E91732E78F5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_46B6597258D351C3882B2BEF277B4F19" xlink:to="loc_us-gaap_SegmentDomain_5C17E281BD0050C8B58E6E91732E78F5" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_CommunicationsMember" xlink:label="loc_mtz_CommunicationsMember_F86B3229287355E9B5448F39BA05675B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_5C17E281BD0050C8B58E6E91732E78F5" xlink:to="loc_mtz_CommunicationsMember_F86B3229287355E9B5448F39BA05675B" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_OilAndGasMember" xlink:label="loc_mtz_OilAndGasMember_A93EA2EA711E5AF0BEF989038B800EBA" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_5C17E281BD0050C8B58E6E91732E78F5" xlink:to="loc_mtz_OilAndGasMember_A93EA2EA711E5AF0BEF989038B800EBA" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_ElectricalTransmissionMember" xlink:label="loc_mtz_ElectricalTransmissionMember_70F7DDEEF3DC5D47836A5DFD8D0DBEFA" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_5C17E281BD0050C8B58E6E91732E78F5" xlink:to="loc_mtz_ElectricalTransmissionMember_70F7DDEEF3DC5D47836A5DFD8D0DBEFA" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_PowerGenerationAndIndustrialMember" xlink:label="loc_mtz_PowerGenerationAndIndustrialMember_70D447B93DA1577EA834569C6DA20C9B" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_5C17E281BD0050C8B58E6E91732E78F5" xlink:to="loc_mtz_PowerGenerationAndIndustrialMember_70D447B93DA1577EA834569C6DA20C9B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AllOtherSegmentsMember" xlink:label="loc_us-gaap_AllOtherSegmentsMember_48CCF95D4A8E5E508525433092062888" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_5C17E281BD0050C8B58E6E91732E78F5" xlink:to="loc_us-gaap_AllOtherSegmentsMember_48CCF95D4A8E5E508525433092062888" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConcentrationRiskByTypeAxis" xlink:label="loc_us-gaap_ConcentrationRiskByTypeAxis_F15933458DFD59B58DFB033E7A90AB4C" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_4538938C868459B8BF7F6398D04EE6CD" xlink:to="loc_us-gaap_ConcentrationRiskByTypeAxis_F15933458DFD59B58DFB033E7A90AB4C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConcentrationRiskTypeDomain" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_8E1E2EC51A66A87B116705C9BC5BD5E6_8FF700ECD19F568F86EB052BB273C9DB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_F15933458DFD59B58DFB033E7A90AB4C" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_8E1E2EC51A66A87B116705C9BC5BD5E6_8FF700ECD19F568F86EB052BB273C9DB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConcentrationRiskTypeDomain" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_2DC3BAB97D5A5923B5320656D6EF90FB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_F15933458DFD59B58DFB033E7A90AB4C" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_2DC3BAB97D5A5923B5320656D6EF90FB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CustomerConcentrationRiskMember" xlink:label="loc_us-gaap_CustomerConcentrationRiskMember_0FEA9B6713F552418429C52783646260" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_2DC3BAB97D5A5923B5320656D6EF90FB" xlink:to="loc_us-gaap_CustomerConcentrationRiskMember_0FEA9B6713F552418429C52783646260" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConcentrationRiskByBenchmarkAxis" xlink:label="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_482F51D9392B5AB0AD68786B0DA02091" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_4538938C868459B8BF7F6398D04EE6CD" xlink:to="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_482F51D9392B5AB0AD68786B0DA02091" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConcentrationRiskBenchmarkDomain" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_F82BC7E9C21C68D4AD2F05C9BC5CAD66_8FF700ECD19F568F86EB052BB273C9DB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_482F51D9392B5AB0AD68786B0DA02091" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_F82BC7E9C21C68D4AD2F05C9BC5CAD66_8FF700ECD19F568F86EB052BB273C9DB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConcentrationRiskBenchmarkDomain" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_BFFE0B7AF5FC508FAA47D36521FC5742" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_482F51D9392B5AB0AD68786B0DA02091" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_BFFE0B7AF5FC508FAA47D36521FC5742" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SalesRevenueServicesNetMember" xlink:label="loc_us-gaap_SalesRevenueServicesNetMember_35D7F79D336A5557BA458C7726736781" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_BFFE0B7AF5FC508FAA47D36521FC5742" xlink:to="loc_us-gaap_SalesRevenueServicesNetMember_35D7F79D336A5557BA458C7726736781" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_MajorCustomersAxis" xlink:label="loc_us-gaap_MajorCustomersAxis_64928976B8115B5AB1CB26CD241A446A" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_4538938C868459B8BF7F6398D04EE6CD" xlink:to="loc_us-gaap_MajorCustomersAxis_64928976B8115B5AB1CB26CD241A446A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NameOfMajorCustomerDomain" xlink:label="loc_us-gaap_NameOfMajorCustomerDomain_768147D3943594F6C15F05C9BC5CD5F6_8FF700ECD19F568F86EB052BB273C9DB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_MajorCustomersAxis_64928976B8115B5AB1CB26CD241A446A" xlink:to="loc_us-gaap_NameOfMajorCustomerDomain_768147D3943594F6C15F05C9BC5CD5F6_8FF700ECD19F568F86EB052BB273C9DB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NameOfMajorCustomerDomain" xlink:label="loc_us-gaap_NameOfMajorCustomerDomain_77797E5DC96B5E3F8C54E76C1E8D9523" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_MajorCustomersAxis_64928976B8115B5AB1CB26CD241A446A" xlink:to="loc_us-gaap_NameOfMajorCustomerDomain_77797E5DC96B5E3F8C54E76C1E8D9523" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_UtilitiesMember" xlink:label="loc_mtz_UtilitiesMember_7DC4BBEFF2935D128F43D1F096841F8A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NameOfMajorCustomerDomain_77797E5DC96B5E3F8C54E76C1E8D9523" xlink:to="loc_mtz_UtilitiesMember_7DC4BBEFF2935D128F43D1F096841F8A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SegmentReportingInformationRevenueAbstract" xlink:label="loc_us-gaap_SegmentReportingInformationRevenueAbstract_72C5B8DFCAB25079A9A02D25E458E33D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_75E8CF7310C351A8A9D2DFAE3C66CEDD" xlink:to="loc_us-gaap_SegmentReportingInformationRevenueAbstract_72C5B8DFCAB25079A9A02D25E458E33D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_Revenues" xlink:label="loc_us-gaap_Revenues_FECCFF945E8D57E0A69D2B2271A02712" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationRevenueAbstract_72C5B8DFCAB25079A9A02D25E458E33D" xlink:to="loc_us-gaap_Revenues_FECCFF945E8D57E0A69D2B2271A02712" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConcentrationRiskPercentage1" xlink:label="loc_us-gaap_ConcentrationRiskPercentage1_511BAD7751C1527788737787BCFBEB2A" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationRevenueAbstract_72C5B8DFCAB25079A9A02D25E458E33D" xlink:to="loc_us-gaap_ConcentrationRiskPercentage1_511BAD7751C1527788737787BCFBEB2A" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.mastec.com/role/SegmentsAndRelatedInformationScheduleOfSignificantCustomersRevenueConcentrationInformationDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SegmentReportingInformationLineItems" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_AD35930300865BDB2273547FB8D3A26E" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfEntityWideRevenueByMajorCustomersByReportingSegmentsTable" xlink:label="loc_us-gaap_ScheduleOfEntityWideRevenueByMajorCustomersByReportingSegmentsTable_75CFA07D78DCD2BCF758547FB8D2D88D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_AD35930300865BDB2273547FB8D3A26E" xlink:to="loc_us-gaap_ScheduleOfEntityWideRevenueByMajorCustomersByReportingSegmentsTable_75CFA07D78DCD2BCF758547FB8D2D88D" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConcentrationRiskByTypeAxis" xlink:label="loc_us-gaap_ConcentrationRiskByTypeAxis_5857B87845EB51F6B419547FB8D2529B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEntityWideRevenueByMajorCustomersByReportingSegmentsTable_75CFA07D78DCD2BCF758547FB8D2D88D" xlink:to="loc_us-gaap_ConcentrationRiskByTypeAxis_5857B87845EB51F6B419547FB8D2529B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConcentrationRiskTypeDomain" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_E29D65872EDDFA9701A1547FB8D2CB72_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_5857B87845EB51F6B419547FB8D2529B" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_E29D65872EDDFA9701A1547FB8D2CB72_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConcentrationRiskTypeDomain" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_E29D65872EDDFA9701A1547FB8D2CB72" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_5857B87845EB51F6B419547FB8D2529B" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_E29D65872EDDFA9701A1547FB8D2CB72" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CustomerConcentrationRiskMember" xlink:label="loc_us-gaap_CustomerConcentrationRiskMember_5377AC1D483DEB3C586D547FB8D3047D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_E29D65872EDDFA9701A1547FB8D2CB72" xlink:to="loc_us-gaap_CustomerConcentrationRiskMember_5377AC1D483DEB3C586D547FB8D3047D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConcentrationRiskByBenchmarkAxis" xlink:label="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_14311459CB8A832CEC75547FB8D3D825" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEntityWideRevenueByMajorCustomersByReportingSegmentsTable_75CFA07D78DCD2BCF758547FB8D2D88D" xlink:to="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_14311459CB8A832CEC75547FB8D3D825" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConcentrationRiskBenchmarkDomain" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_AF5CA995AA8B398E86DC547FB8D394EE_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_14311459CB8A832CEC75547FB8D3D825" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_AF5CA995AA8B398E86DC547FB8D394EE_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConcentrationRiskBenchmarkDomain" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_AF5CA995AA8B398E86DC547FB8D394EE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_14311459CB8A832CEC75547FB8D3D825" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_AF5CA995AA8B398E86DC547FB8D394EE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SalesRevenueServicesNetMember" xlink:label="loc_us-gaap_SalesRevenueServicesNetMember_8DED825F16F42D0A6625547FB8D30AEC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_AF5CA995AA8B398E86DC547FB8D394EE" xlink:to="loc_us-gaap_SalesRevenueServicesNetMember_8DED825F16F42D0A6625547FB8D30AEC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_StatementBusinessSegmentsAxis" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_4593D64896D83DFEDBA4547FB8D386F2" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEntityWideRevenueByMajorCustomersByReportingSegmentsTable_75CFA07D78DCD2BCF758547FB8D2D88D" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_4593D64896D83DFEDBA4547FB8D386F2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SegmentDomain" xlink:label="loc_us-gaap_SegmentDomain_832054CE234E401D559B547FB8D389A2_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_4593D64896D83DFEDBA4547FB8D386F2" xlink:to="loc_us-gaap_SegmentDomain_832054CE234E401D559B547FB8D389A2_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SegmentDomain" xlink:label="loc_us-gaap_SegmentDomain_832054CE234E401D559B547FB8D389A2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_4593D64896D83DFEDBA4547FB8D386F2" xlink:to="loc_us-gaap_SegmentDomain_832054CE234E401D559B547FB8D389A2" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_CommunicationsMember" xlink:label="loc_mtz_CommunicationsMember_8C960D0348E4B6C35D6D547FB8D36A3E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_832054CE234E401D559B547FB8D389A2" xlink:to="loc_mtz_CommunicationsMember_8C960D0348E4B6C35D6D547FB8D36A3E" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_OilAndGasMember" xlink:label="loc_mtz_OilAndGasMember_779EF4D70913A36058C0547FB8D3948D" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_832054CE234E401D559B547FB8D389A2" xlink:to="loc_mtz_OilAndGasMember_779EF4D70913A36058C0547FB8D3948D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_MajorCustomersAxis" xlink:label="loc_us-gaap_MajorCustomersAxis_882168394F97AC41CD91547FB8D30006" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEntityWideRevenueByMajorCustomersByReportingSegmentsTable_75CFA07D78DCD2BCF758547FB8D2D88D" xlink:to="loc_us-gaap_MajorCustomersAxis_882168394F97AC41CD91547FB8D30006" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NameOfMajorCustomerDomain" xlink:label="loc_us-gaap_NameOfMajorCustomerDomain_0434E20508021105FEAE547FB8D3707E_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_MajorCustomersAxis_882168394F97AC41CD91547FB8D30006" xlink:to="loc_us-gaap_NameOfMajorCustomerDomain_0434E20508021105FEAE547FB8D3707E_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NameOfMajorCustomerDomain" xlink:label="loc_us-gaap_NameOfMajorCustomerDomain_0434E20508021105FEAE547FB8D3707E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_MajorCustomersAxis_882168394F97AC41CD91547FB8D30006" xlink:to="loc_us-gaap_NameOfMajorCustomerDomain_0434E20508021105FEAE547FB8D3707E" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_ATT1Member" xlink:label="loc_mtz_ATT1Member_BA1C12D36DE6A317373D547FB8D3A1B0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NameOfMajorCustomerDomain_0434E20508021105FEAE547FB8D3707E" xlink:to="loc_mtz_ATT1Member_BA1C12D36DE6A317373D547FB8D3A1B0" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_EnergyTransferAffiliatesMember" xlink:label="loc_mtz_EnergyTransferAffiliatesMember_0887F1171F83ACAE740A547FB8D38EBC" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NameOfMajorCustomerDomain_0434E20508021105FEAE547FB8D3707E" xlink:to="loc_mtz_EnergyTransferAffiliatesMember_0887F1171F83ACAE740A547FB8D38EBC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConcentrationRiskPercentage1" xlink:label="loc_us-gaap_ConcentrationRiskPercentage1_3A0DAC10DB77D8ABF772547FB8D300B8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_AD35930300865BDB2273547FB8D3A26E" xlink:to="loc_us-gaap_ConcentrationRiskPercentage1_3A0DAC10DB77D8ABF772547FB8D300B8" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.mastec.com/role/SegmentsAndRelatedInformationTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.mastec.com/role/StockBasedCompensationAndOtherEmployeeBenefitPlans" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.mastec.com/role/StockBasedCompensationAndOtherEmployeeBenefitPlansEmployeeStockPurchasePlansNarrativeDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_FBF3ADADE8641AFDA205CFDEA3E48D74" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_A1D653FB61344D77C4A6CFDEA3E37DAC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_FBF3ADADE8641AFDA205CFDEA3E48D74" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_A1D653FB61344D77C4A6CFDEA3E37DAC" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AwardTypeAxis" xlink:label="loc_us-gaap_AwardTypeAxis_0D7DBF720731CEBA2AB2CFDEA3E3A366" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_A1D653FB61344D77C4A6CFDEA3E37DAC" xlink:to="loc_us-gaap_AwardTypeAxis_0D7DBF720731CEBA2AB2CFDEA3E3A366" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_6B5BC12FA0D4926B7EBBCFDEA3E4631A_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_0D7DBF720731CEBA2AB2CFDEA3E3A366" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_6B5BC12FA0D4926B7EBBCFDEA3E4631A_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_6B5BC12FA0D4926B7EBBCFDEA3E4631A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_0D7DBF720731CEBA2AB2CFDEA3E3A366" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_6B5BC12FA0D4926B7EBBCFDEA3E4631A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EmployeeStockMember" xlink:label="loc_us-gaap_EmployeeStockMember_7FEBBEC88E20B637618DCFDEA3E4E695" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_6B5BC12FA0D4926B7EBBCFDEA3E4631A" xlink:to="loc_us-gaap_EmployeeStockMember_7FEBBEC88E20B637618DCFDEA3E4E695" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardDescription" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardDescription_C770F8EE3D763F724B01CFDEA3E48084" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_FBF3ADADE8641AFDA205CFDEA3E48D74" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardDescription_C770F8EE3D763F724B01CFDEA3E48084" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.mastec.com/role/StockBasedCompensationAndOtherEmployeeBenefitPlansNarrativeDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_9CEC32E4FB65DE09593CCFDEA3F28F9E" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_9398C68A8F2267393AE6CFDEA3F2B3F9" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_9CEC32E4FB65DE09593CCFDEA3F28F9E" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_9398C68A8F2267393AE6CFDEA3F2B3F9" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_StatementEquityComponentsAxis" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_C0601B8C4EFB19FD74F3CFDEA3F275A3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_9398C68A8F2267393AE6CFDEA3F2B3F9" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_C0601B8C4EFB19FD74F3CFDEA3F275A3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaap_EquityComponentDomain_30185FF092F76C17B47DCFDEA3F22C20_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_C0601B8C4EFB19FD74F3CFDEA3F275A3" xlink:to="loc_us-gaap_EquityComponentDomain_30185FF092F76C17B47DCFDEA3F22C20_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaap_EquityComponentDomain_30185FF092F76C17B47DCFDEA3F22C20" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_C0601B8C4EFB19FD74F3CFDEA3F275A3" xlink:to="loc_us-gaap_EquityComponentDomain_30185FF092F76C17B47DCFDEA3F22C20" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CommonStockMember" xlink:label="loc_us-gaap_CommonStockMember_BD46D047CBEC4F9698F2CFDEA3F2C47D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_30185FF092F76C17B47DCFDEA3F22C20" xlink:to="loc_us-gaap_CommonStockMember_BD46D047CBEC4F9698F2CFDEA3F2C47D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_8BB8CD0FCB796CC68596CFDEA3F235F2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_9CEC32E4FB65DE09593CCFDEA3F28F9E" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_8BB8CD0FCB796CC68596CFDEA3F235F2" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.mastec.com/role/StockBasedCompensationAndOtherEmployeeBenefitPlansRestrictedSharesNarrativeDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_D11A435D1BD86E10BFB6CFDEA3EF6195" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_793C8BA84A3436571EE3CFDEA3EE7918" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_D11A435D1BD86E10BFB6CFDEA3EF6195" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_793C8BA84A3436571EE3CFDEA3EE7918" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AwardTypeAxis" xlink:label="loc_us-gaap_AwardTypeAxis_A2DC27801EEE8044070ECFDEA3EFC539" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_793C8BA84A3436571EE3CFDEA3EE7918" xlink:to="loc_us-gaap_AwardTypeAxis_A2DC27801EEE8044070ECFDEA3EFC539" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_36A26785A775D9B4E4B5CFDEA3EF0A5C_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_A2DC27801EEE8044070ECFDEA3EFC539" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_36A26785A775D9B4E4B5CFDEA3EF0A5C_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_36A26785A775D9B4E4B5CFDEA3EF0A5C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_A2DC27801EEE8044070ECFDEA3EFC539" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_36A26785A775D9B4E4B5CFDEA3EF0A5C" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_RestrictedStockAndRestrictedStockUnitsMember" xlink:label="loc_mtz_RestrictedStockAndRestrictedStockUnitsMember_C88F28AA088DA3C46231CFDEA3EF621B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_36A26785A775D9B4E4B5CFDEA3EF0A5C" xlink:to="loc_mtz_RestrictedStockAndRestrictedStockUnitsMember_C88F28AA088DA3C46231CFDEA3EF621B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions_474B2EE545C83B98FD00CFDEA3EF0449" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_D11A435D1BD86E10BFB6CFDEA3EF6195" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions_474B2EE545C83B98FD00CFDEA3EF0449" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_1F86F938DD92D26BC51BCFDEA3EF26BF" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_D11A435D1BD86E10BFB6CFDEA3EF6195" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_1F86F938DD92D26BC51BCFDEA3EF26BF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue_96193246B1339B1C4DA2CFDEA3EF8443" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_D11A435D1BD86E10BFB6CFDEA3EF6195" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue_96193246B1339B1C4DA2CFDEA3EF8443" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.mastec.com/role/StockBasedCompensationAndOtherEmployeeBenefitPlansScheduleOfActivityEmployeeStockPurchasePlansDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_8A617C0864325187513B63550A3B5915" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_BB070F6650397D53B60363550A3BC78C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_8A617C0864325187513B63550A3B5915" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_BB070F6650397D53B60363550A3BC78C" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AwardTypeAxis" xlink:label="loc_us-gaap_AwardTypeAxis_166436D760FEF9EBCE4663550A3BB89D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_BB070F6650397D53B60363550A3BC78C" xlink:to="loc_us-gaap_AwardTypeAxis_166436D760FEF9EBCE4663550A3BB89D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_40F841E1D97D0F14491F63550A3BD38C_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_166436D760FEF9EBCE4663550A3BB89D" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_40F841E1D97D0F14491F63550A3BD38C_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_40F841E1D97D0F14491F63550A3BD38C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_166436D760FEF9EBCE4663550A3BB89D" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_40F841E1D97D0F14491F63550A3BD38C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EmployeeStockMember" xlink:label="loc_us-gaap_EmployeeStockMember_2773E90E481B48DD7FCD63550A3BBF79" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_40F841E1D97D0F14491F63550A3BD38C" xlink:to="loc_us-gaap_EmployeeStockMember_2773E90E481B48DD7FCD63550A3BBF79" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_StatementEquityComponentsAxis" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_9E7436BE48D6BA7ED2A663550A3B5694" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_BB070F6650397D53B60363550A3BC78C" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_9E7436BE48D6BA7ED2A663550A3B5694" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaap_EquityComponentDomain_8592182B288ED759974963550A3B7983_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_9E7436BE48D6BA7ED2A663550A3B5694" xlink:to="loc_us-gaap_EquityComponentDomain_8592182B288ED759974963550A3B7983_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaap_EquityComponentDomain_8592182B288ED759974963550A3B7983" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_9E7436BE48D6BA7ED2A663550A3B5694" xlink:to="loc_us-gaap_EquityComponentDomain_8592182B288ED759974963550A3B7983" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CommonStockMember" xlink:label="loc_us-gaap_CommonStockMember_2913FDA3773D7491F69163550A3BF036" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_8592182B288ED759974963550A3B7983" xlink:to="loc_us-gaap_CommonStockMember_2913FDA3773D7491F69163550A3BF036" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlans" xlink:label="loc_us-gaap_ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlans_F60358D5099ADFB627E563550A3B0942" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_8A617C0864325187513B63550A3B5915" xlink:to="loc_us-gaap_ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlans_F60358D5099ADFB627E563550A3B0942" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans_F9BA8D8F7D0FE8BBB5E063550A3BBD4D" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_8A617C0864325187513B63550A3B5915" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans_F9BA8D8F7D0FE8BBB5E063550A3BBD4D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice_375E0D76DB4548E008CD63550A3B0794" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_8A617C0864325187513B63550A3B5915" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice_375E0D76DB4548E008CD63550A3B0794" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_6190694F4BF4D776F88E63550A3BA65D" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_8A617C0864325187513B63550A3B5915" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_6190694F4BF4D776F88E63550A3BA65D" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.mastec.com/role/StockBasedCompensationAndOtherEmployeeBenefitPlansScheduleOfActivityRestrictedSharesDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_69476AF8C22DCC1FFA119B4F7765447F" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_9CCCE053187130BE62539B4F77648F35" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_69476AF8C22DCC1FFA119B4F7765447F" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_9CCCE053187130BE62539B4F77648F35" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_StatementEquityComponentsAxis" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_D4091EC42F7B55D38E149B4F77659907" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_9CCCE053187130BE62539B4F77648F35" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_D4091EC42F7B55D38E149B4F77659907" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaap_EquityComponentDomain_E460688F7953A647D46D9B4F7765A038_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_D4091EC42F7B55D38E149B4F77659907" xlink:to="loc_us-gaap_EquityComponentDomain_E460688F7953A647D46D9B4F7765A038_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaap_EquityComponentDomain_E460688F7953A647D46D9B4F7765A038" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_D4091EC42F7B55D38E149B4F77659907" xlink:to="loc_us-gaap_EquityComponentDomain_E460688F7953A647D46D9B4F7765A038" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CommonStockMember" xlink:label="loc_us-gaap_CommonStockMember_E838DEFE5DAC6D6911FE9B4F776567AA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_E460688F7953A647D46D9B4F7765A038" xlink:to="loc_us-gaap_CommonStockMember_E838DEFE5DAC6D6911FE9B4F776567AA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AwardTypeAxis" xlink:label="loc_us-gaap_AwardTypeAxis_2EA46AE5BC89B0C38B4C9B4F7765CB2D" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_9CCCE053187130BE62539B4F77648F35" xlink:to="loc_us-gaap_AwardTypeAxis_2EA46AE5BC89B0C38B4C9B4F7765CB2D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_7A32EBA1E66F77DCC3939B4F7765B386_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_2EA46AE5BC89B0C38B4C9B4F7765CB2D" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_7A32EBA1E66F77DCC3939B4F7765B386_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_7A32EBA1E66F77DCC3939B4F7765B386" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_2EA46AE5BC89B0C38B4C9B4F7765CB2D" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_7A32EBA1E66F77DCC3939B4F7765B386" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_RestrictedStockAndRestrictedStockUnitsMember" xlink:label="loc_mtz_RestrictedStockAndRestrictedStockUnitsMember_7B6B32FEE0945FD3FA289B4F776594FC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_7A32EBA1E66F77DCC3939B4F7765B386" xlink:to="loc_mtz_RestrictedStockAndRestrictedStockUnitsMember_7B6B32FEE0945FD3FA289B4F776594FC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RestrictedStockUnitsRSUMember" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_9136D3BC3678612F93DE9B4F776527E1" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_7A32EBA1E66F77DCC3939B4F7765B386" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_9136D3BC3678612F93DE9B4F776527E1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_E573135EE383D5FB7B949B4F77653E86" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_69476AF8C22DCC1FFA119B4F7765447F" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_E573135EE383D5FB7B949B4F77653E86" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_4A9E29D27E0861355CB99B4F77656A8C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_E573135EE383D5FB7B949B4F77653E86" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_4A9E29D27E0861355CB99B4F77656A8C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_951D8F62FBF5363C3FFC9B4F77651E1D" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_E573135EE383D5FB7B949B4F77653E86" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_951D8F62FBF5363C3FFC9B4F77651E1D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_53B40FC931FB6F57CA339B4F7765721F" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_E573135EE383D5FB7B949B4F77653E86" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_53B40FC931FB6F57CA339B4F7765721F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_EABA03331553FEB74F629B4F77655EC6" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_E573135EE383D5FB7B949B4F77653E86" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_EABA03331553FEB74F629B4F77655EC6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_6A5133698E9ABE7E471E9B4F77658227" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_69476AF8C22DCC1FFA119B4F7765447F" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_6A5133698E9ABE7E471E9B4F77658227" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_80089412359A09940E2B9B4F7765143B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_6A5133698E9ABE7E471E9B4F77658227" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_80089412359A09940E2B9B4F7765143B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_6AC993860C72EB30F4149B4F77654041" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_6A5133698E9ABE7E471E9B4F77658227" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_6AC993860C72EB30F4149B4F77654041" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_C72AEC4D4B996137B63F9B4F77664157" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_6A5133698E9ABE7E471E9B4F77658227" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_C72AEC4D4B996137B63F9B4F77664157" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_ED7C07AD93B05AA5B7859B4F7766A5A7" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_6A5133698E9ABE7E471E9B4F77658227" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_ED7C07AD93B05AA5B7859B4F7766A5A7" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.mastec.com/role/StockBasedCompensationAndOtherEmployeeBenefitPlansScheduleOfNonCashStockBasedCompensationExpenseAndRelatedTaxEffectsDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_22F2139F26C833FDE947B6A20F8D6A7E" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_BE50BF04D7BEA323C0B1B6A20F8C9F11" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_22F2139F26C833FDE947B6A20F8D6A7E" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_BE50BF04D7BEA323C0B1B6A20F8C9F11" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncomeStatementLocationAxis" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_59631F9F471019635BF9B6A20F8CF72E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_BE50BF04D7BEA323C0B1B6A20F8C9F11" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_59631F9F471019635BF9B6A20F8CF72E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_45EB3510DEB8EB12B152B6A20F8CCF9E_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_59631F9F471019635BF9B6A20F8CF72E" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_45EB3510DEB8EB12B152B6A20F8CCF9E_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_45EB3510DEB8EB12B152B6A20F8CCF9E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_59631F9F471019635BF9B6A20F8CF72E" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_45EB3510DEB8EB12B152B6A20F8CCF9E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_GeneralAndAdministrativeExpenseMember" xlink:label="loc_us-gaap_GeneralAndAdministrativeExpenseMember_19336FA164F05AD0553DB6A20F8C4977" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_45EB3510DEB8EB12B152B6A20F8CCF9E" xlink:to="loc_us-gaap_GeneralAndAdministrativeExpenseMember_19336FA164F05AD0553DB6A20F8C4977" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ProspectiveAdoptionOfNewAccountingPronouncementsAxis" xlink:label="loc_us-gaap_ProspectiveAdoptionOfNewAccountingPronouncementsAxis_FB8A8E3ADF02675CFAECB6A20F8D6321" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_BE50BF04D7BEA323C0B1B6A20F8C9F11" xlink:to="loc_us-gaap_ProspectiveAdoptionOfNewAccountingPronouncementsAxis_FB8A8E3ADF02675CFAECB6A20F8D6321" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AccountingGuidanceMember" xlink:label="loc_us-gaap_AccountingGuidanceMember_4F3E8A1838B9BAC7632CB6A20F8D9878_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ProspectiveAdoptionOfNewAccountingPronouncementsAxis_FB8A8E3ADF02675CFAECB6A20F8D6321" xlink:to="loc_us-gaap_AccountingGuidanceMember_4F3E8A1838B9BAC7632CB6A20F8D9878_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AccountingGuidanceMember" xlink:label="loc_us-gaap_AccountingGuidanceMember_4F3E8A1838B9BAC7632CB6A20F8D9878" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ProspectiveAdoptionOfNewAccountingPronouncementsAxis_FB8A8E3ADF02675CFAECB6A20F8D6321" xlink:to="loc_us-gaap_AccountingGuidanceMember_4F3E8A1838B9BAC7632CB6A20F8D9878" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AccountingStandardsUpdate201609Member" xlink:label="loc_us-gaap_AccountingStandardsUpdate201609Member_B77D703C737B1DDFF215B6A20F8D2C2E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccountingGuidanceMember_4F3E8A1838B9BAC7632CB6A20F8D9878" xlink:to="loc_us-gaap_AccountingStandardsUpdate201609Member_B77D703C737B1DDFF215B6A20F8D2C2E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AllocatedShareBasedCompensationExpense" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_2AC7992C6769138C2D65B6A20F8DA552" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_22F2139F26C833FDE947B6A20F8D6A7E" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_2AC7992C6769138C2D65B6A20F8DA552" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationAggregateDisclosuresAbstract" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationAggregateDisclosuresAbstract_AB51C4C051B30D00471BB6A20F8D27EA" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_22F2139F26C833FDE947B6A20F8D6A7E" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationAggregateDisclosuresAbstract_AB51C4C051B30D00471BB6A20F8D27EA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense_6074D8F78DD5B57BCFAEB6A20F8DED1E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationAggregateDisclosuresAbstract_AB51C4C051B30D00471BB6A20F8D27EA" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense_6074D8F78DD5B57BCFAEB6A20F8DED1E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ExcessTaxBenefitFromShareBasedCompensationOperatingActivities" xlink:label="loc_us-gaap_ExcessTaxBenefitFromShareBasedCompensationOperatingActivities_F0ECEDF38924AF52E309B6A20F8DC975" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationAggregateDisclosuresAbstract_AB51C4C051B30D00471BB6A20F8D27EA" xlink:to="loc_us-gaap_ExcessTaxBenefitFromShareBasedCompensationOperatingActivities_F0ECEDF38924AF52E309B6A20F8DC975" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncomeTaxExpenseBenefit" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_3B0BAD757061DC464E2CB6A20F8D061D" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationAggregateDisclosuresAbstract_AB51C4C051B30D00471BB6A20F8D27EA" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_3B0BAD757061DC464E2CB6A20F8D061D" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.mastec.com/role/StockBasedCompensationAndOtherEmployeeBenefitPlansTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.mastec.com/role/SupplementalGuarantorFinancialInformation" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.mastec.com/role/SupplementalGuarantorFinancialInformationCondensedUnauditedConsolidatingBalanceSheetsDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CondensedBalanceSheetStatementsCaptionsLineItems" xlink:label="loc_us-gaap_CondensedBalanceSheetStatementsCaptionsLineItems_07A51418AC0E58808E3F53A2A1F92ABE" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CondensedBalanceSheetStatementTable" xlink:label="loc_us-gaap_CondensedBalanceSheetStatementTable_C9C18AA82E8F5D6BAD6E860259548E7E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_CondensedBalanceSheetStatementsCaptionsLineItems_07A51418AC0E58808E3F53A2A1F92ABE" xlink:to="loc_us-gaap_CondensedBalanceSheetStatementTable_C9C18AA82E8F5D6BAD6E860259548E7E" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConsolidationItemsAxis" xlink:label="loc_us-gaap_ConsolidationItemsAxis_02729987282F5D2AA78F874785F908E2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_CondensedBalanceSheetStatementTable_C9C18AA82E8F5D6BAD6E860259548E7E" xlink:to="loc_us-gaap_ConsolidationItemsAxis_02729987282F5D2AA78F874785F908E2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConsolidationItemsDomain" xlink:label="loc_us-gaap_ConsolidationItemsDomain_1B5B57BC0E76E167175A05C9BF1A14FC_8FF700ECD19F568F86EB052BB273C9DB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConsolidationItemsAxis_02729987282F5D2AA78F874785F908E2" xlink:to="loc_us-gaap_ConsolidationItemsDomain_1B5B57BC0E76E167175A05C9BF1A14FC_8FF700ECD19F568F86EB052BB273C9DB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConsolidationItemsDomain" xlink:label="loc_us-gaap_ConsolidationItemsDomain_C4D4FF6A025D5DF799840730132943D7" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConsolidationItemsAxis_02729987282F5D2AA78F874785F908E2" xlink:to="loc_us-gaap_ConsolidationItemsDomain_C4D4FF6A025D5DF799840730132943D7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ReportableLegalEntitiesMember" xlink:label="loc_us-gaap_ReportableLegalEntitiesMember_42B97BF5C5FD5AD9A1B0A68A017B0929" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConsolidationItemsDomain_C4D4FF6A025D5DF799840730132943D7" xlink:to="loc_us-gaap_ReportableLegalEntitiesMember_42B97BF5C5FD5AD9A1B0A68A017B0929" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConsolidationEliminationsMember" xlink:label="loc_us-gaap_ConsolidationEliminationsMember_A1EA37C85C965D579FCAADD7081DF67D" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConsolidationItemsDomain_C4D4FF6A025D5DF799840730132943D7" xlink:to="loc_us-gaap_ConsolidationEliminationsMember_A1EA37C85C965D579FCAADD7081DF67D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConsolidatedEntitiesAxis" xlink:label="loc_us-gaap_ConsolidatedEntitiesAxis_AF7808C6B6D153FD832E5996EE4AE79A" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_CondensedBalanceSheetStatementTable_C9C18AA82E8F5D6BAD6E860259548E7E" xlink:to="loc_us-gaap_ConsolidatedEntitiesAxis_AF7808C6B6D153FD832E5996EE4AE79A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConsolidatedEntitiesDomain" xlink:label="loc_us-gaap_ConsolidatedEntitiesDomain_7C5BE28A607A409C2AA405C9BF1BB2FB_8FF700ECD19F568F86EB052BB273C9DB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConsolidatedEntitiesAxis_AF7808C6B6D153FD832E5996EE4AE79A" xlink:to="loc_us-gaap_ConsolidatedEntitiesDomain_7C5BE28A607A409C2AA405C9BF1BB2FB_8FF700ECD19F568F86EB052BB273C9DB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConsolidatedEntitiesDomain" xlink:label="loc_us-gaap_ConsolidatedEntitiesDomain_A461E8D4CCE75FA7858889DF141E53E0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConsolidatedEntitiesAxis_AF7808C6B6D153FD832E5996EE4AE79A" xlink:to="loc_us-gaap_ConsolidatedEntitiesDomain_A461E8D4CCE75FA7858889DF141E53E0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ParentCompanyMember" xlink:label="loc_us-gaap_ParentCompanyMember_8F39AA35D16D5AC9A8621A3E539B730B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConsolidatedEntitiesDomain_A461E8D4CCE75FA7858889DF141E53E0" xlink:to="loc_us-gaap_ParentCompanyMember_8F39AA35D16D5AC9A8621A3E539B730B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_GuarantorSubsidiariesMember" xlink:label="loc_us-gaap_GuarantorSubsidiariesMember_10F2AA8F67E05E49BF2383B8B9F10CD4" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConsolidatedEntitiesDomain_A461E8D4CCE75FA7858889DF141E53E0" xlink:to="loc_us-gaap_GuarantorSubsidiariesMember_10F2AA8F67E05E49BF2383B8B9F10CD4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NonGuarantorSubsidiariesMember" xlink:label="loc_us-gaap_NonGuarantorSubsidiariesMember_9AFF78B406F3578A9FE734F7E9E53FB8" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConsolidatedEntitiesDomain_A461E8D4CCE75FA7858889DF141E53E0" xlink:to="loc_us-gaap_NonGuarantorSubsidiariesMember_9AFF78B406F3578A9FE734F7E9E53FB8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AssetsAbstract" xlink:label="loc_us-gaap_AssetsAbstract_95C87B76359359D6B84F260F7B07E582" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CondensedBalanceSheetStatementsCaptionsLineItems_07A51418AC0E58808E3F53A2A1F92ABE" xlink:to="loc_us-gaap_AssetsAbstract_95C87B76359359D6B84F260F7B07E582" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AssetsCurrent" xlink:label="loc_us-gaap_AssetsCurrent_E4662FBC5DEE5747A36819061479A04F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_95C87B76359359D6B84F260F7B07E582" xlink:to="loc_us-gaap_AssetsCurrent_E4662FBC5DEE5747A36819061479A04F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PropertyPlantAndEquipmentNet" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_52185667A8395D66880492AE4A6D6E6E" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_95C87B76359359D6B84F260F7B07E582" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_52185667A8395D66880492AE4A6D6E6E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IntangibleAssetsNetIncludingGoodwill" xlink:label="loc_us-gaap_IntangibleAssetsNetIncludingGoodwill_8A3B34279D2B54F28034AED5E9B1FEBB" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_95C87B76359359D6B84F260F7B07E582" xlink:to="loc_us-gaap_IntangibleAssetsNetIncludingGoodwill_8A3B34279D2B54F28034AED5E9B1FEBB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DueFromAffiliateNoncurrent" xlink:label="loc_us-gaap_DueFromAffiliateNoncurrent_9F7AFE64DD1C5768B41A9250FFD32973" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_95C87B76359359D6B84F260F7B07E582" xlink:to="loc_us-gaap_DueFromAffiliateNoncurrent_9F7AFE64DD1C5768B41A9250FFD32973" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_OtherAssetsNoncurrent" xlink:label="loc_us-gaap_OtherAssetsNoncurrent_DF28D4CD33BF5E0A8DA07DF268BB169D" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_95C87B76359359D6B84F260F7B07E582" xlink:to="loc_us-gaap_OtherAssetsNoncurrent_DF28D4CD33BF5E0A8DA07DF268BB169D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_Assets" xlink:label="loc_us-gaap_Assets_0C32F5CD1895542E8F0317B95E7463C5" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_95C87B76359359D6B84F260F7B07E582" xlink:to="loc_us-gaap_Assets_0C32F5CD1895542E8F0317B95E7463C5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LiabilitiesAndStockholdersEquityAbstract" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_891514AFD8655BF9B2B3CD28FA71CC75" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CondensedBalanceSheetStatementsCaptionsLineItems_07A51418AC0E58808E3F53A2A1F92ABE" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_891514AFD8655BF9B2B3CD28FA71CC75" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LiabilitiesCurrent" xlink:label="loc_us-gaap_LiabilitiesCurrent_334FA0FB9E2050FDB98EEE74B1A73C0F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_891514AFD8655BF9B2B3CD28FA71CC75" xlink:to="loc_us-gaap_LiabilitiesCurrent_334FA0FB9E2050FDB98EEE74B1A73C0F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LongTermDebtAndCapitalLeaseObligations" xlink:label="loc_us-gaap_LongTermDebtAndCapitalLeaseObligations_9A1A0C91D8495C6FB1F08077BCD46007" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_891514AFD8655BF9B2B3CD28FA71CC75" xlink:to="loc_us-gaap_LongTermDebtAndCapitalLeaseObligations_9A1A0C91D8495C6FB1F08077BCD46007" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LiabilitiesOtherThanLongtermDebtNoncurrent" xlink:label="loc_us-gaap_LiabilitiesOtherThanLongtermDebtNoncurrent_6C5D3417BEA05340B984491E030A4916" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_891514AFD8655BF9B2B3CD28FA71CC75" xlink:to="loc_us-gaap_LiabilitiesOtherThanLongtermDebtNoncurrent_6C5D3417BEA05340B984491E030A4916" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_Liabilities" xlink:label="loc_us-gaap_Liabilities_9DAFE46C03D752DCB0E8FFD6F2659DEA" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_891514AFD8655BF9B2B3CD28FA71CC75" xlink:to="loc_us-gaap_Liabilities_9DAFE46C03D752DCB0E8FFD6F2659DEA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_89327C8F8C9A5B8B90C741A18D9455E2" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_891514AFD8655BF9B2B3CD28FA71CC75" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_89327C8F8C9A5B8B90C741A18D9455E2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LiabilitiesAndStockholdersEquity" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquity_AB5E55E9E32152419E1C68D72A9777EC" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_891514AFD8655BF9B2B3CD28FA71CC75" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquity_AB5E55E9E32152419E1C68D72A9777EC" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.mastec.com/role/SupplementalGuarantorFinancialInformationCondensedUnauditedConsolidatingStatementsOfCashFlowsDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CondensedCashFlowStatementsCaptionsLineItems" xlink:label="loc_us-gaap_CondensedCashFlowStatementsCaptionsLineItems_6B82ADA9E23C2A98D9840F2D2293EAC9" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CondensedCashFlowStatementTable" xlink:label="loc_us-gaap_CondensedCashFlowStatementTable_661E87502C70EFC065590F2D22925B39" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_CondensedCashFlowStatementsCaptionsLineItems_6B82ADA9E23C2A98D9840F2D2293EAC9" xlink:to="loc_us-gaap_CondensedCashFlowStatementTable_661E87502C70EFC065590F2D22925B39" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConsolidationItemsAxis" xlink:label="loc_us-gaap_ConsolidationItemsAxis_A3E913CDA18E43A754130F2D2292959E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_CondensedCashFlowStatementTable_661E87502C70EFC065590F2D22925B39" xlink:to="loc_us-gaap_ConsolidationItemsAxis_A3E913CDA18E43A754130F2D2292959E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConsolidationItemsDomain" xlink:label="loc_us-gaap_ConsolidationItemsDomain_244CB5247A86D26C1A140F2D22927B4E_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConsolidationItemsAxis_A3E913CDA18E43A754130F2D2292959E" xlink:to="loc_us-gaap_ConsolidationItemsDomain_244CB5247A86D26C1A140F2D22927B4E_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConsolidationItemsDomain" xlink:label="loc_us-gaap_ConsolidationItemsDomain_244CB5247A86D26C1A140F2D22927B4E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConsolidationItemsAxis_A3E913CDA18E43A754130F2D2292959E" xlink:to="loc_us-gaap_ConsolidationItemsDomain_244CB5247A86D26C1A140F2D22927B4E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ReportableLegalEntitiesMember" xlink:label="loc_us-gaap_ReportableLegalEntitiesMember_90BFD507C4A8764667310F2D22929E7D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConsolidationItemsDomain_244CB5247A86D26C1A140F2D22927B4E" xlink:to="loc_us-gaap_ReportableLegalEntitiesMember_90BFD507C4A8764667310F2D22929E7D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConsolidationEliminationsMember" xlink:label="loc_us-gaap_ConsolidationEliminationsMember_191D4FB24353585959400F2D2292040F" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConsolidationItemsDomain_244CB5247A86D26C1A140F2D22927B4E" xlink:to="loc_us-gaap_ConsolidationEliminationsMember_191D4FB24353585959400F2D2292040F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConsolidatedEntitiesAxis" xlink:label="loc_us-gaap_ConsolidatedEntitiesAxis_913A063A4D572E0D87640F2D2292D875" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_CondensedCashFlowStatementTable_661E87502C70EFC065590F2D22925B39" xlink:to="loc_us-gaap_ConsolidatedEntitiesAxis_913A063A4D572E0D87640F2D2292D875" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConsolidatedEntitiesDomain" xlink:label="loc_us-gaap_ConsolidatedEntitiesDomain_5012DB7A15703A0DD8880F2D22924BF8_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConsolidatedEntitiesAxis_913A063A4D572E0D87640F2D2292D875" xlink:to="loc_us-gaap_ConsolidatedEntitiesDomain_5012DB7A15703A0DD8880F2D22924BF8_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConsolidatedEntitiesDomain" xlink:label="loc_us-gaap_ConsolidatedEntitiesDomain_5012DB7A15703A0DD8880F2D22924BF8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConsolidatedEntitiesAxis_913A063A4D572E0D87640F2D2292D875" xlink:to="loc_us-gaap_ConsolidatedEntitiesDomain_5012DB7A15703A0DD8880F2D22924BF8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ParentCompanyMember" xlink:label="loc_us-gaap_ParentCompanyMember_D95E087C83E3A34F56390F2D2293CBFC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConsolidatedEntitiesDomain_5012DB7A15703A0DD8880F2D22924BF8" xlink:to="loc_us-gaap_ParentCompanyMember_D95E087C83E3A34F56390F2D2293CBFC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_GuarantorSubsidiariesMember" xlink:label="loc_us-gaap_GuarantorSubsidiariesMember_AB202BE6B16F9386E0D00F2D22930A0F" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConsolidatedEntitiesDomain_5012DB7A15703A0DD8880F2D22924BF8" xlink:to="loc_us-gaap_GuarantorSubsidiariesMember_AB202BE6B16F9386E0D00F2D22930A0F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NonGuarantorSubsidiariesMember" xlink:label="loc_us-gaap_NonGuarantorSubsidiariesMember_27D65EBA6DF552C4DDE60F2D22932BF3" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConsolidatedEntitiesDomain_5012DB7A15703A0DD8880F2D22924BF8" xlink:to="loc_us-gaap_NonGuarantorSubsidiariesMember_27D65EBA6DF552C4DDE60F2D22932BF3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_1C4D3EA570CE1A3537420F2D229374E8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CondensedCashFlowStatementsCaptionsLineItems_6B82ADA9E23C2A98D9840F2D2293EAC9" xlink:to="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_1C4D3EA570CE1A3537420F2D229374E8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_C96354BF9AF5ADAB6A940F2D2293B234" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CondensedCashFlowStatementsCaptionsLineItems_6B82ADA9E23C2A98D9840F2D2293EAC9" xlink:to="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_C96354BF9AF5ADAB6A940F2D2293B234" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired" xlink:label="loc_us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired_0C272F9088255D37FF740F2D2293E066" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_C96354BF9AF5ADAB6A940F2D2293B234" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired_0C272F9088255D37FF740F2D2293E066" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PaymentsToAcquireProductiveAssets" xlink:label="loc_us-gaap_PaymentsToAcquireProductiveAssets_B065E25A6E79D8743CEC0F2D229309E6" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_C96354BF9AF5ADAB6A940F2D2293B234" xlink:to="loc_us-gaap_PaymentsToAcquireProductiveAssets_B065E25A6E79D8743CEC0F2D229309E6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment" xlink:label="loc_us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment_25D67DF94E1A1182BF4F0F2D2293611F" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_C96354BF9AF5ADAB6A940F2D2293B234" xlink:to="loc_us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment_25D67DF94E1A1182BF4F0F2D2293611F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PaymentsToAcquireOtherInvestments" xlink:label="loc_us-gaap_PaymentsToAcquireOtherInvestments_81A76E82E0C539A4486C0F2D2293FC0B" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_C96354BF9AF5ADAB6A940F2D2293B234" xlink:to="loc_us-gaap_PaymentsToAcquireOtherInvestments_81A76E82E0C539A4486C0F2D2293FC0B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ProceedsFromSaleAndMaturityOfOtherInvestments" xlink:label="loc_us-gaap_ProceedsFromSaleAndMaturityOfOtherInvestments_FED648B15623C964EB6F0F2D2293414A" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_C96354BF9AF5ADAB6A940F2D2293B234" xlink:to="loc_us-gaap_ProceedsFromSaleAndMaturityOfOtherInvestments_FED648B15623C964EB6F0F2D2293414A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivities" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_BFAD7729160D5F127B710F2D2293FDBB" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_C96354BF9AF5ADAB6A940F2D2293B234" xlink:to="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_BFAD7729160D5F127B710F2D2293FDBB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_076D5C65B8D54F85CD7A0F2D2294E8A2" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CondensedCashFlowStatementsCaptionsLineItems_6B82ADA9E23C2A98D9840F2D2293EAC9" xlink:to="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_076D5C65B8D54F85CD7A0F2D2294E8A2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ProceedsFromLongTermLinesOfCredit" xlink:label="loc_us-gaap_ProceedsFromLongTermLinesOfCredit_5F0DD6E4F316323CFD260F2D2294685D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_076D5C65B8D54F85CD7A0F2D2294E8A2" xlink:to="loc_us-gaap_ProceedsFromLongTermLinesOfCredit_5F0DD6E4F316323CFD260F2D2294685D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RepaymentsOfLongTermLinesOfCredit" xlink:label="loc_us-gaap_RepaymentsOfLongTermLinesOfCredit_2C622CA971409F59B4D50F2D2294CEBA" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_076D5C65B8D54F85CD7A0F2D2294E8A2" xlink:to="loc_us-gaap_RepaymentsOfLongTermLinesOfCredit_2C622CA971409F59B4D50F2D2294CEBA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RepaymentsOfOtherDebt" xlink:label="loc_us-gaap_RepaymentsOfOtherDebt_C1ABCD0B8D65E1072C520F2D2294AD07" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_076D5C65B8D54F85CD7A0F2D2294E8A2" xlink:to="loc_us-gaap_RepaymentsOfOtherDebt_C1ABCD0B8D65E1072C520F2D2294AD07" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PaymentsForRepurchaseOfCommonStock" xlink:label="loc_us-gaap_PaymentsForRepurchaseOfCommonStock_145F6A983C7ECCAE82760F2D2294677D" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_076D5C65B8D54F85CD7A0F2D2294E8A2" xlink:to="loc_us-gaap_PaymentsForRepurchaseOfCommonStock_145F6A983C7ECCAE82760F2D2294677D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PaymentsToMinorityShareholders" xlink:label="loc_us-gaap_PaymentsToMinorityShareholders_416FA90984BAED7EEFA30F2D2294F9AA" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_076D5C65B8D54F85CD7A0F2D2294E8A2" xlink:to="loc_us-gaap_PaymentsToMinorityShareholders_416FA90984BAED7EEFA30F2D2294F9AA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlansIncludingStockOptions" xlink:label="loc_us-gaap_ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlansIncludingStockOptions_E14B93CD8898C2CC824D0F2D2294516F" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_076D5C65B8D54F85CD7A0F2D2294E8A2" xlink:to="loc_us-gaap_ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlansIncludingStockOptions_E14B93CD8898C2CC824D0F2D2294516F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation" xlink:label="loc_us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation_FE03D060F48418445A020F2D2294D0C9" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_076D5C65B8D54F85CD7A0F2D2294E8A2" xlink:to="loc_us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation_FE03D060F48418445A020F2D2294D0C9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ProceedsFromPaymentsForOtherFinancingActivities" xlink:label="loc_us-gaap_ProceedsFromPaymentsForOtherFinancingActivities_7A70F646F3B63EF238650F2D2294EE77" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_076D5C65B8D54F85CD7A0F2D2294E8A2" xlink:to="loc_us-gaap_ProceedsFromPaymentsForOtherFinancingActivities_7A70F646F3B63EF238650F2D2294EE77" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_NetFinancingActivitiesAndAdvancesFromToConsolidatedAffiliates" xlink:label="loc_mtz_NetFinancingActivitiesAndAdvancesFromToConsolidatedAffiliates_97A5DDB1BA96227CDB600F2D2294338A" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_076D5C65B8D54F85CD7A0F2D2294E8A2" xlink:to="loc_mtz_NetFinancingActivitiesAndAdvancesFromToConsolidatedAffiliates_97A5DDB1BA96227CDB600F2D2294338A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivities" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_A10CEC76BAF3A9850D260F2D22942245" xlink:type="locator" />
    <link:definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_076D5C65B8D54F85CD7A0F2D2294E8A2" xlink:to="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_A10CEC76BAF3A9850D260F2D22942245" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EffectOfExchangeRateOnCashAndCashEquivalents" xlink:label="loc_us-gaap_EffectOfExchangeRateOnCashAndCashEquivalents_49C459C6FFB3A6FBA4060F2D2294DD66" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CondensedCashFlowStatementsCaptionsLineItems_6B82ADA9E23C2A98D9840F2D2293EAC9" xlink:to="loc_us-gaap_EffectOfExchangeRateOnCashAndCashEquivalents_49C459C6FFB3A6FBA4060F2D2294DD66" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease" xlink:label="loc_us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease_897AFC518697CB503E370F2D2294151D" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CondensedCashFlowStatementsCaptionsLineItems_6B82ADA9E23C2A98D9840F2D2293EAC9" xlink:to="loc_us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease_897AFC518697CB503E370F2D2294151D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_AF9C234DD7F2917C31780F2D229405CD" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CondensedCashFlowStatementsCaptionsLineItems_6B82ADA9E23C2A98D9840F2D2293EAC9" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_AF9C234DD7F2917C31780F2D229405CD" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.mastec.com/role/SupplementalGuarantorFinancialInformationCondensedUnauditedConsolidatingStatementsOfOperationsAndComprehensiveIncomeLossDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CondensedIncomeStatementsCaptionsLineItems" xlink:label="loc_us-gaap_CondensedIncomeStatementsCaptionsLineItems_A24EA877EFF94E515DD7CFDEA2FDA577" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CondensedIncomeStatementTable" xlink:label="loc_us-gaap_CondensedIncomeStatementTable_EE89F3B3B78EB09B13A8CFDEA2FC2C5A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_CondensedIncomeStatementsCaptionsLineItems_A24EA877EFF94E515DD7CFDEA2FDA577" xlink:to="loc_us-gaap_CondensedIncomeStatementTable_EE89F3B3B78EB09B13A8CFDEA2FC2C5A" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConsolidationItemsAxis" xlink:label="loc_us-gaap_ConsolidationItemsAxis_5A530222A2D0399A87B2CFDEA2FC90FD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_CondensedIncomeStatementTable_EE89F3B3B78EB09B13A8CFDEA2FC2C5A" xlink:to="loc_us-gaap_ConsolidationItemsAxis_5A530222A2D0399A87B2CFDEA2FC90FD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConsolidationItemsDomain" xlink:label="loc_us-gaap_ConsolidationItemsDomain_ADC8625DB4558842DA18CFDEA2FC220A_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConsolidationItemsAxis_5A530222A2D0399A87B2CFDEA2FC90FD" xlink:to="loc_us-gaap_ConsolidationItemsDomain_ADC8625DB4558842DA18CFDEA2FC220A_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConsolidationItemsDomain" xlink:label="loc_us-gaap_ConsolidationItemsDomain_ADC8625DB4558842DA18CFDEA2FC220A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConsolidationItemsAxis_5A530222A2D0399A87B2CFDEA2FC90FD" xlink:to="loc_us-gaap_ConsolidationItemsDomain_ADC8625DB4558842DA18CFDEA2FC220A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ReportableLegalEntitiesMember" xlink:label="loc_us-gaap_ReportableLegalEntitiesMember_80DF8A7D74970A5FEE86CFDEA2FC0A1B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConsolidationItemsDomain_ADC8625DB4558842DA18CFDEA2FC220A" xlink:to="loc_us-gaap_ReportableLegalEntitiesMember_80DF8A7D74970A5FEE86CFDEA2FC0A1B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConsolidationEliminationsMember" xlink:label="loc_us-gaap_ConsolidationEliminationsMember_F59AB20A85FD295CB9A0CFDEA2FCFAB6" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConsolidationItemsDomain_ADC8625DB4558842DA18CFDEA2FC220A" xlink:to="loc_us-gaap_ConsolidationEliminationsMember_F59AB20A85FD295CB9A0CFDEA2FCFAB6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConsolidatedEntitiesAxis" xlink:label="loc_us-gaap_ConsolidatedEntitiesAxis_74721776497855E68B3BCFDEA2FCD51A" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_CondensedIncomeStatementTable_EE89F3B3B78EB09B13A8CFDEA2FC2C5A" xlink:to="loc_us-gaap_ConsolidatedEntitiesAxis_74721776497855E68B3BCFDEA2FCD51A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConsolidatedEntitiesDomain" xlink:label="loc_us-gaap_ConsolidatedEntitiesDomain_053FB2918410D64B6A54CFDEA2FC0270_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConsolidatedEntitiesAxis_74721776497855E68B3BCFDEA2FCD51A" xlink:to="loc_us-gaap_ConsolidatedEntitiesDomain_053FB2918410D64B6A54CFDEA2FC0270_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConsolidatedEntitiesDomain" xlink:label="loc_us-gaap_ConsolidatedEntitiesDomain_053FB2918410D64B6A54CFDEA2FC0270" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConsolidatedEntitiesAxis_74721776497855E68B3BCFDEA2FCD51A" xlink:to="loc_us-gaap_ConsolidatedEntitiesDomain_053FB2918410D64B6A54CFDEA2FC0270" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ParentCompanyMember" xlink:label="loc_us-gaap_ParentCompanyMember_BE8BF5FCEBDEC263A4CBCFDEA2FC6DE9" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConsolidatedEntitiesDomain_053FB2918410D64B6A54CFDEA2FC0270" xlink:to="loc_us-gaap_ParentCompanyMember_BE8BF5FCEBDEC263A4CBCFDEA2FC6DE9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_GuarantorSubsidiariesMember" xlink:label="loc_us-gaap_GuarantorSubsidiariesMember_ED1F26929EE73A60B31CCFDEA2FDA55A" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConsolidatedEntitiesDomain_053FB2918410D64B6A54CFDEA2FC0270" xlink:to="loc_us-gaap_GuarantorSubsidiariesMember_ED1F26929EE73A60B31CCFDEA2FDA55A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NonGuarantorSubsidiariesMember" xlink:label="loc_us-gaap_NonGuarantorSubsidiariesMember_FAE6B0DB1BE3466BD93FCFDEA2FDD655" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConsolidatedEntitiesDomain_053FB2918410D64B6A54CFDEA2FC0270" xlink:to="loc_us-gaap_NonGuarantorSubsidiariesMember_FAE6B0DB1BE3466BD93FCFDEA2FDD655" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_Revenues" xlink:label="loc_us-gaap_Revenues_8A77DF4292F83357F13DCFDEA2FD821C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CondensedIncomeStatementsCaptionsLineItems_A24EA877EFF94E515DD7CFDEA2FDA577" xlink:to="loc_us-gaap_Revenues_8A77DF4292F83357F13DCFDEA2FD821C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CostOfServicesExcludingDepreciationDepletionAndAmortization" xlink:label="loc_us-gaap_CostOfServicesExcludingDepreciationDepletionAndAmortization_29CCA859132ED21D936DCFDEA2FDFB4B" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CondensedIncomeStatementsCaptionsLineItems_A24EA877EFF94E515DD7CFDEA2FDA577" xlink:to="loc_us-gaap_CostOfServicesExcludingDepreciationDepletionAndAmortization_29CCA859132ED21D936DCFDEA2FDFB4B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DepreciationDepletionAndAmortization" xlink:label="loc_us-gaap_DepreciationDepletionAndAmortization_B3790DCB558483C3E53ACFDEA2FD2E6C" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CondensedIncomeStatementsCaptionsLineItems_A24EA877EFF94E515DD7CFDEA2FDA577" xlink:to="loc_us-gaap_DepreciationDepletionAndAmortization_B3790DCB558483C3E53ACFDEA2FD2E6C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_GeneralAndAdministrativeExpense" xlink:label="loc_us-gaap_GeneralAndAdministrativeExpense_C5E09C329BFB3B9E0B07CFDEA2FDFFC9" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CondensedIncomeStatementsCaptionsLineItems_A24EA877EFF94E515DD7CFDEA2FDA577" xlink:to="loc_us-gaap_GeneralAndAdministrativeExpense_C5E09C329BFB3B9E0B07CFDEA2FDFFC9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_InterestRevenueExpenseNet" xlink:label="loc_us-gaap_InterestRevenueExpenseNet_2F02AF3B46904AC60A6CCFDEA2FD1C99" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CondensedIncomeStatementsCaptionsLineItems_A24EA877EFF94E515DD7CFDEA2FDA577" xlink:to="loc_us-gaap_InterestRevenueExpenseNet_2F02AF3B46904AC60A6CCFDEA2FD1C99" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncomeLossFromEquityMethodInvestments" xlink:label="loc_us-gaap_IncomeLossFromEquityMethodInvestments_02DA315BE9D56FA16AAFCFDEA2FD266C" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CondensedIncomeStatementsCaptionsLineItems_A24EA877EFF94E515DD7CFDEA2FDA577" xlink:to="loc_us-gaap_IncomeLossFromEquityMethodInvestments_02DA315BE9D56FA16AAFCFDEA2FD266C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NonoperatingIncomeExpense" xlink:label="loc_us-gaap_NonoperatingIncomeExpense_0E9AD99966B2C7654280CFDEA2FDD93A" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CondensedIncomeStatementsCaptionsLineItems_A24EA877EFF94E515DD7CFDEA2FDA577" xlink:to="loc_us-gaap_NonoperatingIncomeExpense_0E9AD99966B2C7654280CFDEA2FDD93A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_1C043A527AA9BBF79990CFDEA2FD4F38" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CondensedIncomeStatementsCaptionsLineItems_A24EA877EFF94E515DD7CFDEA2FDA577" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_1C043A527AA9BBF79990CFDEA2FD4F38" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncomeTaxExpenseBenefit" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_F72BB2715E1EF9DC5E63CFDEA2FDB8AC" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CondensedIncomeStatementsCaptionsLineItems_A24EA877EFF94E515DD7CFDEA2FDA577" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_F72BB2715E1EF9DC5E63CFDEA2FDB8AC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest_9E7B43E1F1C360CFFDC2CFDEA2FD06A8" xlink:type="locator" />
    <link:definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CondensedIncomeStatementsCaptionsLineItems_A24EA877EFF94E515DD7CFDEA2FDA577" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest_9E7B43E1F1C360CFFDC2CFDEA2FD06A8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncomeLossFromSubsidiariesNetOfTax" xlink:label="loc_us-gaap_IncomeLossFromSubsidiariesNetOfTax_5C45D4DA5F157A9E4547CFDEA2FDF54C" xlink:type="locator" />
    <link:definitionArc order="11" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CondensedIncomeStatementsCaptionsLineItems_A24EA877EFF94E515DD7CFDEA2FDA577" xlink:to="loc_us-gaap_IncomeLossFromSubsidiariesNetOfTax_5C45D4DA5F157A9E4547CFDEA2FDF54C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ProfitLoss" xlink:label="loc_us-gaap_ProfitLoss_785C24CF1B27C78A5A8ECFDEA2FEBDD4" xlink:type="locator" />
    <link:definitionArc order="12" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CondensedIncomeStatementsCaptionsLineItems_A24EA877EFF94E515DD7CFDEA2FDA577" xlink:to="loc_us-gaap_ProfitLoss_785C24CF1B27C78A5A8ECFDEA2FEBDD4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NetIncomeLossAttributableToNoncontrollingInterest" xlink:label="loc_us-gaap_NetIncomeLossAttributableToNoncontrollingInterest_9622FBDEAAB45D089A7CCFDEA2FEFCFE" xlink:type="locator" />
    <link:definitionArc order="13" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CondensedIncomeStatementsCaptionsLineItems_A24EA877EFF94E515DD7CFDEA2FDA577" xlink:to="loc_us-gaap_NetIncomeLossAttributableToNoncontrollingInterest_9622FBDEAAB45D089A7CCFDEA2FEFCFE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NetIncomeLoss" xlink:label="loc_us-gaap_NetIncomeLoss_C865354C229BD0893105CFDEA2FE1FF9" xlink:type="locator" />
    <link:definitionArc order="14" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CondensedIncomeStatementsCaptionsLineItems_A24EA877EFF94E515DD7CFDEA2FDA577" xlink:to="loc_us-gaap_NetIncomeLoss_C865354C229BD0893105CFDEA2FE1FF9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest" xlink:label="loc_us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest_A37C5CA639383B34645ECFDEA2FE7EAA" xlink:type="locator" />
    <link:definitionArc order="15" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CondensedIncomeStatementsCaptionsLineItems_A24EA877EFF94E515DD7CFDEA2FDA577" xlink:to="loc_us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest_A37C5CA639383B34645ECFDEA2FE7EAA" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.mastec.com/role/SupplementalGuarantorFinancialInformationNarrativeDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:label="loc_us-gaap_CondensedFinancialStatementsCaptionsLineItems_464584B7DC0459288C2E6904C841B8DF" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfCondensedFinancialStatementsTable" xlink:label="loc_us-gaap_ScheduleOfCondensedFinancialStatementsTable_27952402DA0D5CE389A093F58ABFA80F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_CondensedFinancialStatementsCaptionsLineItems_464584B7DC0459288C2E6904C841B8DF" xlink:to="loc_us-gaap_ScheduleOfCondensedFinancialStatementsTable_27952402DA0D5CE389A093F58ABFA80F" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LongtermDebtTypeAxis" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_F19B189674EF5003ABB758AD587C2E37" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfCondensedFinancialStatementsTable_27952402DA0D5CE389A093F58ABFA80F" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_F19B189674EF5003ABB758AD587C2E37" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_EC26497445D231FA09C705C9BE143966_8FF700ECD19F568F86EB052BB273C9DB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_F19B189674EF5003ABB758AD587C2E37" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_EC26497445D231FA09C705C9BE143966_8FF700ECD19F568F86EB052BB273C9DB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_A8EC987C09A75369897435C8C4CEC0F2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_F19B189674EF5003ABB758AD587C2E37" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_A8EC987C09A75369897435C8C4CEC0F2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SeniorNotesMember" xlink:label="loc_us-gaap_SeniorNotesMember_370126A0C75F51ECA22DF175ED7225B5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_A8EC987C09A75369897435C8C4CEC0F2" xlink:to="loc_us-gaap_SeniorNotesMember_370126A0C75F51ECA22DF175ED7225B5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentAxis" xlink:label="loc_us-gaap_DebtInstrumentAxis_DC6BC9BE42835447A3AC135B023632D9" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfCondensedFinancialStatementsTable_27952402DA0D5CE389A093F58ABFA80F" xlink:to="loc_us-gaap_DebtInstrumentAxis_DC6BC9BE42835447A3AC135B023632D9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_9B635F46FF9442A9C1C005C9BE15EE24_8FF700ECD19F568F86EB052BB273C9DB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_DC6BC9BE42835447A3AC135B023632D9" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_9B635F46FF9442A9C1C005C9BE15EE24_8FF700ECD19F568F86EB052BB273C9DB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_9186ED310DB25F368F0D68FD2D996F11" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_DC6BC9BE42835447A3AC135B023632D9" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_9186ED310DB25F368F0D68FD2D996F11" xlink:type="arc" />
    <link:loc xlink:href="mtz-20180331.xsd#mtz_FourPointEightSevenFivePercentSeniorNotesMember" xlink:label="loc_mtz_FourPointEightSevenFivePercentSeniorNotesMember_B7966A034035529FB93E52F20BF02D70" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_9186ED310DB25F368F0D68FD2D996F11" xlink:to="loc_mtz_FourPointEightSevenFivePercentSeniorNotesMember_B7966A034035529FB93E52F20BF02D70" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_F57027B781445937BB797762BA845191" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CondensedFinancialStatementsCaptionsLineItems_464584B7DC0459288C2E6904C841B8DF" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_F57027B781445937BB797762BA845191" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.mastec.com/role/SupplementalGuarantorFinancialInformationTables" xlink:type="extended" />
</link:linkbase>
