

<!-- RR Donnelley Xcelerate Taxonomy Schema, based on XBRL 2.1  http://www.rrdonnelley.com/ -->
<!-- Version: 6.22.4 -->
<!-- Round: 1e4aef1d-63cc-449d-8881-4433525881e3 -->
<!-- Creation date: 2015-11-04T20:32:30Z -->
<!-- Copyright (c) 2005-2013 R.R. Donnelley & Sons Company All Rights Reserved. -->
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        <link:definition>101 - Document - Document and Entity Information</link:definition>
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        <link:definition>109 - Disclosure - Goodwill</link:definition>
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        <link:definition>110 - Disclosure - Business Combinations</link:definition>
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        <link:definition>111 - Disclosure - Income Taxes</link:definition>
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        <link:definition>112 - Disclosure - Net income per ordinary share</link:definition>
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        <link:definition>113 - Disclosure - Share-based Awards</link:definition>
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        <link:definition>114 - Disclosure - Share Capital</link:definition>
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        <link:definition>115 - Disclosure - Business Segment Information</link:definition>
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        <link:definition>116 - Disclosure - Goodwill (Tables)</link:definition>
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        <link:definition>117 - Disclosure - Business Combinations (Tables)</link:definition>
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        <link:definition>118 - Disclosure - Income Taxes (Tables)</link:definition>
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        <link:definition>119 - Disclosure - Net income per ordinary share (Tables)</link:definition>
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        <link:definition>120 - Disclosure - Share-based Awards (Tables)</link:definition>
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        <link:definition>122 - Disclosure - Goodwill (Detail)</link:definition>
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        <link:definition>123 - Disclosure - Business Combinations - Additional Information (Detail)</link:definition>
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        <link:definition>124 - Disclosure - Summary of Estimates of Fair Values of Assets Acquired and Liabilities Assumed of MediMedia Pharma Solutions (Detail)</link:definition>
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        <link:definition>125 - Disclosure - Summary of Estimates of Fair Values of Assets Acquired and Liabilities Assumed of Aptiv Solutions (Detail)</link:definition>
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        <link:definition>126 - Disclosure - Income Taxes Recognized During Period (Detail)</link:definition>
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        <link:definition>127 - Disclosure - Income Taxes - Additional Information (Detail)</link:definition>
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        <link:definition>128 - Disclosure - Reconciliation of Number of Shares Used in Computation of Basic and Diluted Net Income Per Ordinary Share (Detail)</link:definition>
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        <link:definition>129 - Disclosure - Share-based Awards - Additional Information (Detail)</link:definition>
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        <link:definition>130 - Disclosure - Summary of Stock Option Activity (Detail)</link:definition>
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        <link:definition>131 - Disclosure - Summary of Movement in Non-Vested Share Options (Detail)</link:definition>
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        <link:definition>132 - Disclosure - Schedule of Weighted Average Fair Values and Assumptions Used (Detail)</link:definition>
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        <link:definition>133 - Disclosure - Summary of RSU and PSU Activity (Detail)</link:definition>
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        <link:definition>135 - Disclosure - Share Capital - Additional Information (Detail)</link:definition>
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        <link:definition>136 - Disclosure - Distribution of Net Revenue by Geographical Area (Detail)</link:definition>
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        <link:definition>137 - Disclosure - Distribution of Income from Operations, including Restructuring and Other Items, by Geographical Area (Detail)</link:definition>
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        <link:definition>138 - Disclosure - Distribution of Property, Plant and Equipment, Net, by Geographical Area (Detail)</link:definition>
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        <link:definition>139 - Disclosure - Distribution of Depreciation and Amortization by Geographical Area (Detail)</link:definition>
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        <link:definition>140 - Disclosure - Distribution of Total Assets by Geographical Area (Detail)</link:definition>
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  <element name="BuybackProgramMember" id="iclr_BuybackProgramMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="CapitalGovernmentGrantsNoncurrent" id="iclr_CapitalGovernmentGrantsNoncurrent" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="credit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="CapitalRedemptionReserve" id="iclr_CapitalRedemptionReserve" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="credit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="CapitalRedemptionReserveMember" id="iclr_CapitalRedemptionReserveMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="CompensationRelatedCostsShareBasedPaymentsDisclosureLineItems" id="iclr_CompensationRelatedCostsShareBasedPaymentsDisclosureLineItems" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="CompensationRelatedCostsShareBasedPaymentsDisclosureTable" id="iclr_CompensationRelatedCostsShareBasedPaymentsDisclosureTable" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrldt:hypercubeItem"/>
  <element name="DocumentAndEntityInformationAbstract" id="iclr_DocumentAndEntityInformationAbstract" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="EmployeeMember" id="iclr_EmployeeMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="EmployeeStockPlanTwentyZeroEightPlanMember" id="iclr_EmployeeStockPlanTwentyZeroEightPlanMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="EmployeeStockPlanTwentyZeroThreePlanMember" id="iclr_EmployeeStockPlanTwentyZeroThreePlanMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="MediaPharmaSolutionsMember" id="iclr_MediaPharmaSolutionsMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="OperatingIncomeByGeographyTableTextBlock" id="iclr_OperatingIncomeByGeographyTableTextBlock" type="nonnum:textBlockItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="OrderBacklogMember" id="iclr_OrderBacklogMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationAdjustmentBeforeTaxLongTermFunding" id="iclr_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationAdjustmentBeforeTaxLongTermFunding" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="credit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationAdjustmentLongTermFundingTax" id="iclr_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationAdjustmentLongTermFundingTax" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="OtherCountriesMember" id="iclr_OtherCountriesMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="PaymentsForShareRepurchaseCosts" id="iclr_PaymentsForShareRepurchaseCosts" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="credit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="PerformanceShareUnitMember" id="iclr_PerformanceShareUnitMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ProceedsFromStockOptionsAndRestrictedSharesExercised" id="iclr_ProceedsFromStockOptionsAndRestrictedSharesExercised" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ReconciliationOfProvisionOfIncomeTaxesLineItems" id="iclr_ReconciliationOfProvisionOfIncomeTaxesLineItems" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ReconciliationOfProvisionOfIncomeTaxesTable" id="iclr_ReconciliationOfProvisionOfIncomeTaxesTable" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrldt:hypercubeItem"/>
  <element name="RecoveryOfAmortizationOfGovernmentGrants" id="iclr_RecoveryOfAmortizationOfGovernmentGrants" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="credit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="RestOfEuropeMember" id="iclr_RestOfEuropeMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="RestrictedStockUnitsTwentyThirteenMember" id="iclr_RestrictedStockUnitsTwentyThirteenMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="RestrictedStockUnitsTwentyZeroEightMember" id="iclr_RestrictedStockUnitsTwentyZeroEightMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ScheduleOfDepreciationAndAmortizationExpenseByGeographicalAreaTableTextBlock" id="iclr_ScheduleOfDepreciationAndAmortizationExpenseByGeographicalAreaTableTextBlock" type="nonnum:textBlockItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ScheduleOfNonCashStockCompensationExpenseTableTextBlock" id="iclr_ScheduleOfNonCashStockCompensationExpenseTableTextBlock" type="nonnum:textBlockItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ScheduleOfShareBasedCompensationRestrictedStockUnitsPerformanceStockUnitsAwardActivityTableTextBlock" id="iclr_ScheduleOfShareBasedCompensationRestrictedStockUnitsPerformanceStockUnitsAwardActivityTableTextBlock" type="nonnum:textBlockItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ScheduleOfWeightedAverageNumberOfDilutedSharesOutstandingLineItems" id="iclr_ScheduleOfWeightedAverageNumberOfDilutedSharesOutstandingLineItems" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ScheduleOfWeightedAverageNumberOfDilutedSharesOutstandingTable" id="iclr_ScheduleOfWeightedAverageNumberOfDilutedSharesOutstandingTable" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrldt:hypercubeItem"/>
  <element name="SegmentReportingDisclosureLineItems" id="iclr_SegmentReportingDisclosureLineItems" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="SegmentReportingDisclosureTable" id="iclr_SegmentReportingDisclosureTable" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrldt:hypercubeItem"/>
  <element name="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsExpectedToVestNumber" id="iclr_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsExpectedToVestNumber" type="xbrli:sharesItemType" abstract="false" xbrli:periodType="instant" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ShareBasedCompensationArrangementByShareBasedPaymentAwardForfeitedInPeriodWeightedAverageGrantDateFairValue" id="iclr_ShareBasedCompensationArrangementByShareBasedPaymentAwardForfeitedInPeriodWeightedAverageGrantDateFairValue" type="num:perShareItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ShareBasedCompensationArrangementByShareBasedPaymentAwardNonvestedOptionsForfeitedInPeriodWeightedAverageExercisePrice" id="iclr_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonvestedOptionsForfeitedInPeriodWeightedAverageExercisePrice" type="num:perShareItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ShareBasedCompensationArrangementByShareBasedPaymentAwardNonvestedOptionsGrantedInPeriodWeightedAverageExercisePrice" id="iclr_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonvestedOptionsGrantedInPeriodWeightedAverageExercisePrice" type="num:perShareItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ShareBasedCompensationArrangementByShareBasedPaymentAwardNonvestedOptionsOutstandingExercisePriceAbstract" id="iclr_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonvestedOptionsOutstandingExercisePriceAbstract" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
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  <element name="ShareBasedCompensationArrangementByShareBasedPaymentAwardNonvestedOptionsVestedInPeriodWeightedAverageExercisePrice" id="iclr_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonvestedOptionsVestedInPeriodWeightedAverageExercisePrice" type="num:perShareItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageGrantDateFairValue" id="iclr_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageGrantDateFairValue" type="num:perShareItemType" abstract="false" xbrli:periodType="instant" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisedInPeriodWeightedAverageGrantDateFairValue" id="iclr_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisedInPeriodWeightedAverageGrantDateFairValue" type="num:perShareItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingOptionPrice" id="iclr_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingOptionPrice" type="num:perShareItemType" abstract="false" xbrli:periodType="instant" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsWeightedAverageGrantDateFairValue" id="iclr_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsWeightedAverageGrantDateFairValue" type="num:perShareItemType" abstract="false" xbrli:periodType="instant" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsWeightedAverageGrantDateFairValueAbstract" id="iclr_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsWeightedAverageGrantDateFairValueAbstract" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsWeightedAverageRemainingContractualTermAbstract" id="iclr_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsWeightedAverageRemainingContractualTermAbstract" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="UnrecognizedTaxBenefitsCurrentYearTaxPositions" id="iclr_UnrecognizedTaxBenefitsCurrentYearTaxPositions" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="credit" nillable="true" substitutionGroup="xbrli:item"/>
</schema>





