<?xml version="1.0" encoding="US-ASCII"?>
<!--XBRL Document Created with Wdesk from Workiva-->
<!-- -->
<xsd:schema attributeFormDefault="unqualified" elementFormDefault="qualified" targetNamespace="http://www.tandemdiabetes.com/20190630" xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:nonnum="http://www.xbrl.org/dtr/type/non-numeric" xmlns:num="http://www.xbrl.org/dtr/type/numeric" xmlns:tndm="http://www.tandemdiabetes.com/20190630" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xmlns:xbrli="http://www.xbrl.org/2003/instance" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
  <xsd:import namespace="http://fasb.org/srt/2018-01-31" schemaLocation="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd" />
  <xsd:import namespace="http://fasb.org/us-gaap/2018-01-31" schemaLocation="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd" />
  <xsd:import namespace="http://fasb.org/us-roles/2018-01-31" schemaLocation="http://xbrl.fasb.org/us-gaap/2018/elts/us-roles-2018-01-31.xsd" />
  <xsd:import namespace="http://fasb.org/us-types/2018-01-31" schemaLocation="http://xbrl.fasb.org/us-gaap/2018/elts/us-types-2018-01-31.xsd" />
  <xsd:import namespace="http://www.xbrl.org/2003/instance" schemaLocation="http://www.xbrl.org/2003/xbrl-instance-2003-12-31.xsd" />
  <xsd:import namespace="http://www.xbrl.org/2003/linkbase" schemaLocation="http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd" />
  <xsd:import namespace="http://www.xbrl.org/2009/arcrole/fact-explanatoryFact" schemaLocation="http://www.xbrl.org/lrr/arcrole/factExplanatory-2009-12-16.xsd" />
  <xsd:import namespace="http://www.xbrl.org/2009/role/negated" schemaLocation="http://www.xbrl.org/lrr/role/negated-2009-12-16.xsd" />
  <xsd:import namespace="http://www.xbrl.org/2009/role/net" schemaLocation="http://www.xbrl.org/lrr/role/net-2009-12-16.xsd" />
  <xsd:import namespace="http://www.xbrl.org/dtr/type/non-numeric" schemaLocation="http://www.xbrl.org/dtr/type/nonNumeric-2009-12-16.xsd" />
  <xsd:import namespace="http://www.xbrl.org/dtr/type/numeric" schemaLocation="http://www.xbrl.org/dtr/type/numeric-2009-12-16.xsd" />
  <xsd:import namespace="http://xbrl.org/2005/xbrldt" schemaLocation="http://www.xbrl.org/2005/xbrldt-2005.xsd" />
  <xsd:import namespace="http://xbrl.sec.gov/country/2017-01-31" schemaLocation="http://xbrl.sec.gov/country/2017/country-2017-01-31.xsd" />
  <xsd:import namespace="http://xbrl.sec.gov/currency/2017-01-31" schemaLocation="http://xbrl.sec.gov/currency/2017/currency-2017-01-31.xsd" />
  <xsd:import namespace="http://xbrl.sec.gov/dei/2019-01-31" schemaLocation="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd" />
  <xsd:import namespace="http://xbrl.sec.gov/exch/2018-01-31" schemaLocation="https://xbrl.sec.gov/exch/2018/exch-2018-01-31.xsd" />
  <xsd:import namespace="http://xbrl.sec.gov/invest/2013-01-31" schemaLocation="http://xbrl.sec.gov/invest/2013/invest-2013-01-31.xsd" />
  <xsd:import namespace="http://xbrl.sec.gov/naics/2017-01-31" schemaLocation="http://xbrl.sec.gov/naics/2017/naics-2017-01-31.xsd" />
  <xsd:import namespace="http://xbrl.sec.gov/sic/2011-01-31" schemaLocation="http://xbrl.sec.gov/sic/2011/sic-2011-01-31.xsd" />
  <xsd:import namespace="http://xbrl.sec.gov/stpr/2018-01-31" schemaLocation="https://xbrl.sec.gov/stpr/2018/stpr-2018-01-31.xsd" />
  <xsd:annotation>
    <xsd:appinfo>
      <link:linkbaseRef xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="tndm-20190630_cal.xml" xlink:role="http://www.xbrl.org/2003/role/calculationLinkbaseRef" xlink:type="simple" />
      <link:linkbaseRef xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="tndm-20190630_def.xml" xlink:role="http://www.xbrl.org/2003/role/definitionLinkbaseRef" xlink:type="simple" />
      <link:linkbaseRef xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="tndm-20190630_lab.xml" xlink:role="http://www.xbrl.org/2003/role/labelLinkbaseRef" xlink:type="simple" />
      <link:linkbaseRef xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="tndm-20190630_pre.xml" xlink:role="http://www.xbrl.org/2003/role/presentationLinkbaseRef" xlink:type="simple" />
      <link:roleType id="CommitmentsAndContingencies" roleURI="http://www.tandemdiabetes.com/role/CommitmentsAndContingencies">
        <link:definition>2109100 - Disclosure - Commitments and Contingencies</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CommitmentsAndContingenciesAdditionalInformationDetail" roleURI="http://www.tandemdiabetes.com/role/CommitmentsAndContingenciesAdditionalInformationDetail">
        <link:definition>2409401 - Disclosure - Commitments and Contingencies - Additional Information (Detail)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CondensedConsolidatedBalanceSheets" roleURI="http://www.tandemdiabetes.com/role/CondensedConsolidatedBalanceSheets">
        <link:definition>1001000 - Statement - CONDENSED CONSOLIDATED BALANCE SHEETS</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CondensedConsolidatedBalanceSheetsParenthetical" roleURI="http://www.tandemdiabetes.com/role/CondensedConsolidatedBalanceSheetsParenthetical">
        <link:definition>1001501 - Statement - CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CondensedConsolidatedStatementsOfCashFlows" roleURI="http://www.tandemdiabetes.com/role/CondensedConsolidatedStatementsOfCashFlows">
        <link:definition>1004000 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CondensedConsolidatedStatementsOfOperationsAndComprehensiveLoss" roleURI="http://www.tandemdiabetes.com/role/CondensedConsolidatedStatementsOfOperationsAndComprehensiveLoss">
        <link:definition>1002000 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CondensedConsolidatedStatementsOfStockholdersEquityDeficit" roleURI="http://www.tandemdiabetes.com/role/CondensedConsolidatedStatementsOfStockholdersEquityDeficit">
        <link:definition>1003000 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (DEFICIT)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CoverPage" roleURI="http://www.tandemdiabetes.com/role/CoverPage">
        <link:definition>0002000 - Document - Cover Page</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="FairValueMeasurements" roleURI="http://www.tandemdiabetes.com/role/FairValueMeasurements">
        <link:definition>2105100 - Disclosure - Fair Value Measurements</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="FairValueMeasurementsAdditionalInformationDetail" roleURI="http://www.tandemdiabetes.com/role/FairValueMeasurementsAdditionalInformationDetail">
        <link:definition>2405403 - Disclosure - Fair Value Measurements - Additional Information (Detail)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="FairValueMeasurementsScheduleOfAssumptionsUsedToEstimateFairValuesOfCommonStockWarrantsDetail" roleURI="http://www.tandemdiabetes.com/role/FairValueMeasurementsScheduleOfAssumptionsUsedToEstimateFairValuesOfCommonStockWarrantsDetail">
        <link:definition>2405404 - Disclosure - Fair Value Measurements - Schedule of Assumptions Used to Estimate Fair Values of Common Stock Warrants (Detail)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="FairValueMeasurementsScheduleOfFinancialAssetsAndLiabilitiesMeasuredAtFairValueOnRecurringBasisDetail" roleURI="http://www.tandemdiabetes.com/role/FairValueMeasurementsScheduleOfFinancialAssetsAndLiabilitiesMeasuredAtFairValueOnRecurringBasisDetail">
        <link:definition>2405402 - Disclosure - Fair Value Measurements - Schedule of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="FairValueMeasurementsScheduleOfFinancialAssetsAndLiabilitiesMeasuredAtFairValueOnRecurringBasisFootnoteDetail" roleURI="http://www.tandemdiabetes.com/role/FairValueMeasurementsScheduleOfFinancialAssetsAndLiabilitiesMeasuredAtFairValueOnRecurringBasisFootnoteDetail">
        <link:definition>2405406 - Disclosure - Fair Value Measurements - Schedule of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis Footnote (Detail)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="FairValueMeasurementsSummaryOfChangesInFairValueOfTotalLevel3FinancialAssetsDetail" roleURI="http://www.tandemdiabetes.com/role/FairValueMeasurementsSummaryOfChangesInFairValueOfTotalLevel3FinancialAssetsDetail">
        <link:definition>2405405 - Disclosure - Fair Value Measurements - Summary of Changes in Fair Value of Total Level 3 Financial Assets (Detail)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="FairValueMeasurementsTables" roleURI="http://www.tandemdiabetes.com/role/FairValueMeasurementsTables">
        <link:definition>2305301 - Disclosure - Fair Value Measurements (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="Inventories" roleURI="http://www.tandemdiabetes.com/role/Inventories">
        <link:definition>2104100 - Disclosure - Inventories</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="InventoriesSummaryOfInventoriesDetail" roleURI="http://www.tandemdiabetes.com/role/InventoriesSummaryOfInventoriesDetail">
        <link:definition>2404402 - Disclosure - Inventories - Summary of Inventories (Detail)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="InventoriesTables" roleURI="http://www.tandemdiabetes.com/role/InventoriesTables">
        <link:definition>2304301 - Disclosure - Inventories (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="Leases" roleURI="http://www.tandemdiabetes.com/role/Leases">
        <link:definition>2106100 - Disclosure - Leases</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LeasesAdditionalInformationDetail" roleURI="http://www.tandemdiabetes.com/role/LeasesAdditionalInformationDetail">
        <link:definition>2406402 - Disclosure - Leases - Additional Information (Detail)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LeasesLeasesTables" roleURI="http://www.tandemdiabetes.com/role/LeasesLeasesTables">
        <link:definition>2306301 - Disclosure - Leases Leases (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LeasesScheduleOfFutureMinimumPaymentsUnderNonCancellableOperatingLeasesDetails" roleURI="http://www.tandemdiabetes.com/role/LeasesScheduleOfFutureMinimumPaymentsUnderNonCancellableOperatingLeasesDetails">
        <link:definition>2406403 - Disclosure - Leases Schedule of Future Minimum Payments Under Non-cancellable Operating Leases (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LeasesScheduleOfFutureMinimumPaymentsUnderNonCancellableOperatingLeasesDetailsCalc2" roleURI="http://www.tandemdiabetes.com/role/LeasesScheduleOfFutureMinimumPaymentsUnderNonCancellableOperatingLeasesDetailsCalc2">
        <link:definition>2406403 - Disclosure - Leases Schedule of Future Minimum Payments Under Non-cancellable Operating Leases (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="OrganizationAndBasisOfPresentation" roleURI="http://www.tandemdiabetes.com/role/OrganizationAndBasisOfPresentation">
        <link:definition>2101100 - Disclosure - Organization and Basis of Presentation</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="OrganizationAndBasisOfPresentationAdditionalInformationDetail" roleURI="http://www.tandemdiabetes.com/role/OrganizationAndBasisOfPresentationAdditionalInformationDetail">
        <link:definition>2401402 - Disclosure - Organization and Basis of Presentation - Additional Information (Detail)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="OrganizationAndBasisOfPresentationPolicies" roleURI="http://www.tandemdiabetes.com/role/OrganizationAndBasisOfPresentationPolicies">
        <link:definition>2201201 - Disclosure - Organization and Basis of Presentation (Policies)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="ShortTermInvestments" roleURI="http://www.tandemdiabetes.com/role/ShortTermInvestments">
        <link:definition>2103100 - Disclosure - Short-Term Investments</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="ShortTermInvestmentsSummaryOfEstimatedFairValueOfShortTermInvestmentsDetail" roleURI="http://www.tandemdiabetes.com/role/ShortTermInvestmentsSummaryOfEstimatedFairValueOfShortTermInvestmentsDetail">
        <link:definition>2403402 - Disclosure - Short-Term Investments - Summary of Estimated Fair Value of Short-Term Investments (Detail)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="ShortTermInvestmentsTables" roleURI="http://www.tandemdiabetes.com/role/ShortTermInvestmentsTables">
        <link:definition>2303301 - Disclosure - Short-Term Investments (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="StockholdersEquity" roleURI="http://www.tandemdiabetes.com/role/StockholdersEquity">
        <link:definition>2108100 - Disclosure - Stockholders' Equity</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="StockholdersEquityAdditionalInformationDetail" roleURI="http://www.tandemdiabetes.com/role/StockholdersEquityAdditionalInformationDetail">
        <link:definition>2408402 - Disclosure - Stockholders' Equity - Additional Information (Detail)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="StockholdersEquityScheduleOfAssumptionsUsedInBlackScholesOptionPricingModelDetail" roleURI="http://www.tandemdiabetes.com/role/StockholdersEquityScheduleOfAssumptionsUsedInBlackScholesOptionPricingModelDetail">
        <link:definition>2408404 - Disclosure - Stockholders' Equity - Schedule of Assumptions Used in Black-Scholes Option-Pricing Model (Detail)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="StockholdersEquityScheduleOfSharesOfCommonStockReservedForFutureIssuanceDetail" roleURI="http://www.tandemdiabetes.com/role/StockholdersEquityScheduleOfSharesOfCommonStockReservedForFutureIssuanceDetail">
        <link:definition>2408403 - Disclosure - Stockholders' Equity - Schedule of Shares of Common Stock Reserved for Future Issuance (Detail)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="StockholdersEquitySummaryForAllocationOfStockBasedCompensationExpenseDetail" roleURI="http://www.tandemdiabetes.com/role/StockholdersEquitySummaryForAllocationOfStockBasedCompensationExpenseDetail">
        <link:definition>2408405 - Disclosure - Stockholders' Equity - Summary for Allocation of Stock-Based Compensation Expense (Detail)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="StockholdersEquityTables" roleURI="http://www.tandemdiabetes.com/role/StockholdersEquityTables">
        <link:definition>2308301 - Disclosure - Stockholders' Equity (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="SummaryOfSignificantAccountingPolicies" roleURI="http://www.tandemdiabetes.com/role/SummaryOfSignificantAccountingPolicies">
        <link:definition>2102100 - Disclosure - Summary of Significant Accounting Policies</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="SummaryOfSignificantAccountingPoliciesAdditionalInformationDetail" roleURI="http://www.tandemdiabetes.com/role/SummaryOfSignificantAccountingPoliciesAdditionalInformationDetail">
        <link:definition>2402402 - Disclosure - Summary of Significant Accounting Policies - Additional Information (Detail)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="SummaryOfSignificantAccountingPoliciesAdditionalInformationDetail1" roleURI="http://www.tandemdiabetes.com/role/SummaryOfSignificantAccountingPoliciesAdditionalInformationDetail1">
        <link:definition>2402403 - Disclosure - Summary of Significant Accounting Policies - Additional Information (Detail1)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="SummaryOfSignificantAccountingPoliciesScheduleOfAntiDilutiveSecuritiesDetail" roleURI="http://www.tandemdiabetes.com/role/SummaryOfSignificantAccountingPoliciesScheduleOfAntiDilutiveSecuritiesDetail">
        <link:definition>2402405 - Disclosure - Summary of Significant Accounting Policies - Schedule of Anti-Dilutive Securities (Detail)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="SummaryOfSignificantAccountingPoliciesSummaryOfReconciliationOfChangeInProductWarrantyLiabilitiesDetail" roleURI="http://www.tandemdiabetes.com/role/SummaryOfSignificantAccountingPoliciesSummaryOfReconciliationOfChangeInProductWarrantyLiabilitiesDetail">
        <link:definition>2402404 - Disclosure - Summary of Significant Accounting Policies - Summary of Reconciliation of Change in Product Warranty Liabilities (Detail)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="SummaryOfSignificantAccountingPoliciesTables" roleURI="http://www.tandemdiabetes.com/role/SummaryOfSignificantAccountingPoliciesTables">
        <link:definition>2302301 - Disclosure - Summary of Significant Accounting Policies (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="TermLoanAgreement" roleURI="http://www.tandemdiabetes.com/role/TermLoanAgreement">
        <link:definition>2107100 - Disclosure - Term Loan Agreement</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="TermLoanAgreementAdditionalInformationDetail" roleURI="http://www.tandemdiabetes.com/role/TermLoanAgreementAdditionalInformationDetail">
        <link:definition>2407401 - Disclosure - Term Loan Agreement - Additional Information (Detail)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
    </xsd:appinfo>
  </xsd:annotation>
  <xsd:element id="tndm_AllowanceForSalesReturns" name="AllowanceForSalesReturns" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element abstract="true" id="tndm_CashCashEquivalentsAndShortTermInvestmentsLineItems" name="CashCashEquivalentsAndShortTermInvestmentsLineItems" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="tndm_CashCashEquivalentsAndShortTermInvestmentsTable" name="CashCashEquivalentsAndShortTermInvestmentsTable" nillable="true" substitutionGroup="xbrldt:hypercubeItem" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element id="tndm_CashEquivalentsMaturityTerm" name="CashEquivalentsMaturityTerm" nillable="true" substitutionGroup="xbrli:item" type="xbrli:durationItemType" xbrli:periodType="duration" />
  <xsd:element id="tndm_ClassOfWarrantOrRightsOutstandingContractualLife" name="ClassOfWarrantOrRightsOutstandingContractualLife" nillable="true" substitutionGroup="xbrli:item" type="xbrli:durationItemType" xbrli:periodType="duration" />
  <xsd:element id="tndm_ClassofWarrantorRightExpired" name="ClassofWarrantorRightExpired" nillable="true" substitutionGroup="xbrli:item" type="xbrli:sharesItemType" xbrli:periodType="instant" />
  <xsd:element id="tndm_CommonStockWarrants" name="CommonStockWarrants" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element abstract="true" id="tndm_ComplementaryProductsMember" name="ComplementaryProductsMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="tndm_CompoundedInterestRate" name="CompoundedInterestRate" nillable="true" substitutionGroup="xbrli:item" type="num:percentItemType" xbrli:periodType="instant" />
  <xsd:element id="tndm_DebtDiscountIncurredDuringNoncashOrPartialNoncashTransaction" name="DebtDiscountIncurredDuringNoncashOrPartialNoncashTransaction" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element id="tndm_DebtInstrumentDateOfLastRequiredInterestPayment" name="DebtInstrumentDateOfLastRequiredInterestPayment" nillable="true" substitutionGroup="xbrli:item" type="xbrli:dateItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="tndm_December2017Member" name="December2017Member" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="tndm_DifferenceBetweenLeasesGuidanceInEffectBeforeAndAfterTopic842Member" name="DifferenceBetweenLeasesGuidanceInEffectBeforeAndAfterTopic842Member" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="tndm_FairValueOfCommonStockWarrantsAtTimeOfExercise" name="FairValueOfCommonStockWarrantsAtTimeOfExercise" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element id="tndm_FairValueOfWarrantLiability" name="FairValueOfWarrantLiability" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element id="tndm_IncreaseDecreaseInDeferredRent" name="IncreaseDecreaseInDeferredRent" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="tndm_InsulinPumpMember" name="InsulinPumpMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="tndm_InterestRate" name="InterestRate" nillable="true" substitutionGroup="xbrli:item" type="num:percentItemType" xbrli:periodType="instant" />
  <xsd:element id="tndm_IssuanceOfCommonStockInitialPublicOfferingNetOfUnderwritingDiscountsAndCommissions" name="IssuanceOfCommonStockInitialPublicOfferingNetOfUnderwritingDiscountsAndCommissions" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element id="tndm_IssuanceOfCommonStockInitialPublicOfferingNetOfUnderwritingDiscountsAndCommissionsShares" name="IssuanceOfCommonStockInitialPublicOfferingNetOfUnderwritingDiscountsAndCommissionsShares" nillable="true" substitutionGroup="xbrli:item" type="xbrli:sharesItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="tndm_June2018Member" name="June2018Member" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="tndm_LeaseArrangementsAxis" name="LeaseArrangementsAxis" nillable="true" substitutionGroup="xbrldt:dimensionItem" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="tndm_LeaseArrangementsDomain" name="LeaseArrangementsDomain" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="tndm_MarindustryPlaceMember" name="MarindustryPlaceMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="tndm_NumberOfLegalProceedingsRegulatoryMattersOrOtherDisputesOrClaims" name="NumberOfLegalProceedingsRegulatoryMattersOrOtherDisputesOrClaims" nillable="true" substitutionGroup="xbrli:item" type="xbrli:integerItemType" xbrli:periodType="duration" />
  <xsd:element id="tndm_OfferedPeriodForSalesReturnPriorToExpiration" name="OfferedPeriodForSalesReturnPriorToExpiration" nillable="true" substitutionGroup="xbrli:item" type="xbrli:durationItemType" xbrli:periodType="duration" />
  <xsd:element id="tndm_OfferingPeriod" name="OfferingPeriod" nillable="true" substitutionGroup="xbrli:item" type="xbrli:durationItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="tndm_OrganizationAndBasisOfPresentationLineItems" name="OrganizationAndBasisOfPresentationLineItems" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="tndm_OrganizationAndBasisOfPresentationTable" name="OrganizationAndBasisOfPresentationTable" nillable="true" substitutionGroup="xbrldt:hypercubeItem" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element id="tndm_PercentageOfNewPumpShipmentsRepresentedByProductHardwarePlatform" name="PercentageOfNewPumpShipmentsRepresentedByProductHardwarePlatform" nillable="true" substitutionGroup="xbrli:item" type="num:percentItemType" xbrli:periodType="duration" />
  <xsd:element id="tndm_ProceedsFromIssuanceOfSecondaryPublicOfferingGross" name="ProceedsFromIssuanceOfSecondaryPublicOfferingGross" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element id="tndm_ProceedsFromPublicOfferingNetOfOfferingCosts" name="ProceedsFromPublicOfferingNetOfOfferingCosts" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element id="tndm_ProductLifeSpanTerm" name="ProductLifeSpanTerm" nillable="true" substitutionGroup="xbrli:item" type="xbrli:durationItemType" xbrli:periodType="duration" />
  <xsd:element id="tndm_ProductsWarrantyPeriod" name="ProductsWarrantyPeriod" nillable="true" substitutionGroup="xbrli:item" type="xbrli:durationItemType" xbrli:periodType="duration" />
  <xsd:element id="tndm_PublicOfferingPeriod" name="PublicOfferingPeriod" nillable="true" substitutionGroup="xbrli:item" type="xbrli:durationItemType" xbrli:periodType="duration" />
  <xsd:element id="tndm_PurchasePeriod" name="PurchasePeriod" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element id="tndm_ScheduleOfCommonStockReservedForFutureIssuanceTableTextBlock" name="ScheduleOfCommonStockReservedForFutureIssuanceTableTextBlock" nillable="true" substitutionGroup="xbrli:item" type="nonnum:textBlockItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="tndm_SecondaryPublicOfferingMember" name="SecondaryPublicOfferingMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="tndm_SeriesAWarrantsMember" name="SeriesAWarrantsMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="tndm_SharebasedCompensationAwardTrancheFourMember" name="SharebasedCompensationAwardTrancheFourMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="tndm_ShortTermInvestmentsAccumulatedGrossUnrealizedGainBeforeTax" name="ShortTermInvestmentsAccumulatedGrossUnrealizedGainBeforeTax" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element id="tndm_ShortTermInvestmentsAccumulatedGrossUnrealizedLossBeforeTax" name="ShortTermInvestmentsAccumulatedGrossUnrealizedLossBeforeTax" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element id="tndm_ShortTermInvestmentsAmortizedCost" name="ShortTermInvestmentsAmortizedCost" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element id="tndm_ShortTermInvestmentsMaturity" name="ShortTermInvestmentsMaturity" nillable="true" substitutionGroup="xbrli:item" type="xbrli:durationItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="tndm_SlimCartridgesAndInfusionSetsMember" name="SlimCartridgesAndInfusionSetsMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="tndm_StockIssuedDuringPeriodSharesCommonStockWarrantsExercised" name="StockIssuedDuringPeriodSharesCommonStockWarrantsExercised" nillable="true" substitutionGroup="xbrli:item" type="xbrli:sharesItemType" xbrli:periodType="duration" />
  <xsd:element id="tndm_StockIssuedDuringPeriodValueCommonStockWarrantsExercised" name="StockIssuedDuringPeriodValueCommonStockWarrantsExercised" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="tndm_StockOptionsIssuedAndOutstandingMember" name="StockOptionsIssuedAndOutstandingMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="tndm_SummaryOfSignificantAccountingPoliciesLineItems" name="SummaryOfSignificantAccountingPoliciesLineItems" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="tndm_SummaryOfSignificantAccountingPoliciesTable" name="SummaryOfSignificantAccountingPoliciesTable" nillable="true" substitutionGroup="xbrldt:hypercubeItem" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="tndm_TSlimX2Member" name="TSlimX2Member" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="tndm_TandemPumpMember" name="TandemPumpMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="tndm_TermLoanAmendmentsMember" name="TermLoanAmendmentsMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="tndm_TermLoanMember" name="TermLoanMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="tndm_TwoThousandThirteenPlanMember" name="TwoThousandThirteenPlanMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="tndm_VistaSorrentoAmendedLeaseMember" name="VistaSorrentoAmendedLeaseMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="tndm_VistaSorrentoLeaseMember" name="VistaSorrentoLeaseMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="tndm_VistaSorrentoParkwayMember" name="VistaSorrentoParkwayMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
</xsd:schema>
