<?xml version="1.0" encoding="US-ASCII"?>
<!-- DFIN New ActiveDisclosure (SM) XBRL Schema Document - http://www.dfinsolutions.com/ -->
<!-- Creation Date :2026-04-24T15:14:38.3723+00:00 -->
<!-- Copyright (c) 2026 Donnelley Financial Solutions, Inc. All Rights Reserved. -->
<xsd:schema targetNamespace="http://comcastcorp.com/20260424" attributeFormDefault="unqualified" elementFormDefault="qualified" xmlns:dtr-types="http://www.xbrl.org/dtr/type/2024-01-31" xmlns:cmcsa="http://comcastcorp.com/20260424" xmlns:enum2="http://xbrl.org/2020/extensible-enumerations-2.0" xmlns:ecd-sub="http://xbrl.sec.gov/ecd-sub/2025" xmlns:ecd="http://xbrl.sec.gov/ecd/2025" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:us-gaap="http://fasb.org/us-gaap/2025" xmlns:dei="http://xbrl.sec.gov/dei/2025" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xmlns:xbrli="http://www.xbrl.org/2003/instance" xmlns:xlink="http://www.w3.org/1999/xlink">
  <xsd:import schemaLocation="http://www.xbrl.org/2003/xbrl-instance-2003-12-31.xsd" namespace="http://www.xbrl.org/2003/instance"/>
  <xsd:import schemaLocation="http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd" namespace="http://www.xbrl.org/2003/linkbase"/>
  <xsd:import schemaLocation="http://www.xbrl.org/2005/xbrldt-2005.xsd" namespace="http://xbrl.org/2005/xbrldt"/>
  <xsd:import schemaLocation="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd" namespace="http://xbrl.sec.gov/ecd/2025"/>
  <xsd:import schemaLocation="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd" namespace="http://fasb.org/us-gaap/2025"/>
  <xsd:import schemaLocation="https://www.xbrl.org/dtr/type/2024-01-31/types.xsd" namespace="http://www.xbrl.org/dtr/type/2024-01-31"/>
  <xsd:import schemaLocation="https://xbrl.sec.gov/ecd/2025/ecd-sub-2025.xsd" namespace="http://xbrl.sec.gov/ecd-sub/2025"/>
  <xsd:import schemaLocation="https://xbrl.sec.gov/dei/2025/dei-2025.xsd" namespace="http://xbrl.sec.gov/dei/2025"/>
  <xsd:annotation>
    <xsd:appinfo>
      <link:roleType roleURI="http://comcastcorp.com/20260424/taxonomy/role/DocumentDocumentAndEntityInformation" id="DocumentDocumentAndEntityInformation">
        <link:definition>75000 - Document - Document and Entity Information</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:linkbase id="lnk">
        <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:arcroleRef arcroleURI="http://www.esma.europa.eu/xbrl/esef/arcrole/wider-narrower" xlink:href="http://www.xbrl.org/lrr/arcrole/esma-arcrole-2018-11-21.xsd#wider-narrower" xlink:type="simple"/>
        <link:roleRef roleURI="http://xbrl.sec.gov/ecd/role/PvpAdjustmentsOnly" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#PvpAdjustmentsOnly" xlink:type="simple"/>
        <link:roleRef roleURI="http://comcastcorp.com/20260424/taxonomy/role/DocumentDocumentAndEntityInformation" xlink:href="cmcsa-20260424.xsd#DocumentDocumentAndEntityInformation" xlink:type="simple"/>
        <link:roleRef roleURI="http://xbrl.sec.gov/ecd/role/PvpDisclosure" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#PvpDisclosure" xlink:type="simple"/>
        <link:labelLink xlink:role="http://www.xbrl.org/2003/role/link" xlink:title="labelLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_AmendmentFlag" xlink:label="dei_AmendmentFlag"/>
          <link:loc xlink:type="locator" xlink:href="cmcsa-20260424.xsd#cmcsa_TotalShareholderReturnAmountYearOverYearChangePercent" xlink:label="cmcsa_TotalShareholderReturnAmountYearOverYearChangePercent"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentType" xlink:label="dei_DocumentType"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityCentralIndexKey" xlink:label="dei_EntityCentralIndexKey"/>
          <link:loc xlink:type="locator" xlink:href="cmcsa-20260424.xsd#cmcsa_ProfitLossYearOverYearChangePercent" xlink:label="cmcsa_ProfitLossYearOverYearChangePercent"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProfitLoss" xlink:label="us-gaap_ProfitLoss"/>
          <link:loc xlink:type="locator" xlink:href="cmcsa-20260424.xsd#cmcsa_PEOActuallyPaidCompensationAmountYearOverYearChangePercent" xlink:label="cmcsa_PEOActuallyPaidCompensationAmountYearOverYearChangePercent"/>
          <link:loc xlink:type="locator" xlink:href="cmcsa-20260424.xsd#cmcsa_PeerGroupTotalShareholderReturnAmountYearOverYearChangePercent" xlink:label="cmcsa_PeerGroupTotalShareholderReturnAmountYearOverYearChangePercent"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_CoverAbstract" xlink:label="dei_CoverAbstract"/>
          <link:loc xlink:type="locator" xlink:href="cmcsa-20260424.xsd#cmcsa_LessFairValueOfAwardsForfeitedDuringTheCoveredYearMember" xlink:label="cmcsa_LessFairValueOfAwardsForfeitedDuringTheCoveredYearMember"/>
          <link:loc xlink:type="locator" xlink:href="cmcsa-20260424.xsd#cmcsa_CompanySelectedMeasureAmountYearOverYearChangePercent" xlink:label="cmcsa_CompanySelectedMeasureAmountYearOverYearChangePercent"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityRegistrantName" xlink:label="dei_EntityRegistrantName"/>
          <link:loc xlink:type="locator" xlink:href="cmcsa-20260424.xsd#cmcsa_NonPEONEOAverageCompensationActuallyPaidAmountYearOverYearChangePercent" xlink:label="cmcsa_NonPEONEOAverageCompensationActuallyPaidAmountYearOverYearChangePercent"/>
          <link:loc xlink:type="locator" xlink:href="cmcsa-20260424.xsd#cmcsa_NetIncomeLossYearOverYearChangePercent" xlink:label="cmcsa_NetIncomeLossYearOverYearChangePercent"/>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_AmendmentFlag_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Amendment Flag</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="cmcsa_TotalShareholderReturnAmountYearOverYearChangePercent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Company's Cumulative TSR,YOY CHANGE</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="cmcsa_TotalShareholderReturnAmountYearOverYearChangePercent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Total Shareholder Return Amount Year Over Year Change Percent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="cmcsa_TotalShareholderReturnAmountYearOverYearChangePercent_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">total shareholder return amount year over year change percent.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentType_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Document Type</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityCentralIndexKey_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Central Index Key</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="cmcsa_ProfitLossYearOverYearChangePercent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Profit Loss Year Over Year Change Percent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="cmcsa_ProfitLossYearOverYearChangePercent_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Profit loss year over year change percent.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="cmcsa_ProfitLossYearOverYearChangePercent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Profit Loss, YOY CHANGE</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProfitLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Net Income (Loss), Including Portion Attributable to Noncontrolling Interest</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProfitLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Net Income (Loss), Including Portion Attributable to Noncontrolling Interest, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProfitLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net Income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="cmcsa_PEOActuallyPaidCompensationAmountYearOverYearChangePercent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">PEO Actually Paid Compensation Amount Year Over Year Change Percent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="cmcsa_PEOActuallyPaidCompensationAmountYearOverYearChangePercent_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">PEO actually paid compensation amount year over year change percent.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="cmcsa_PEOActuallyPaidCompensationAmountYearOverYearChangePercent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Compensation "Actually Paid" to PEO, YOY CHANGE</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="cmcsa_PeerGroupTotalShareholderReturnAmountYearOverYearChangePercent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Peer Group Cumulative TSR, YOY CHANGE</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="cmcsa_PeerGroupTotalShareholderReturnAmountYearOverYearChangePercent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Peer Group Total Shareholder Return Amount Year Over Year Change Percent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="cmcsa_PeerGroupTotalShareholderReturnAmountYearOverYearChangePercent_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Peer Group Total Shareholder Return Amount Year Over Year Change Percent.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_CoverAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cover [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="cmcsa_LessFairValueOfAwardsForfeitedDuringTheCoveredYearMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Less Fair Value Of Awards Forfeited During The Covered Year [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="cmcsa_LessFairValueOfAwardsForfeitedDuringTheCoveredYearMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Less Fair Value Of Awards Forfeited During The Covered Year [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="cmcsa_CompanySelectedMeasureAmountYearOverYearChangePercent_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">company selected measure amount year over year change percent.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="cmcsa_CompanySelectedMeasureAmountYearOverYearChangePercent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">CompanySelectedMeasureAmountYearOverYearChangePercent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="cmcsa_CompanySelectedMeasureAmountYearOverYearChangePercent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Adjusted EBITDA, YOY CHANGE</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityRegistrantName_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Registrant Name</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="cmcsa_NonPEONEOAverageCompensationActuallyPaidAmountYearOverYearChangePercent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Non PEO NEO Average Compensation Actually Paid Amount Year Over Year Change Percent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="cmcsa_NonPEONEOAverageCompensationActuallyPaidAmountYearOverYearChangePercent_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Non pEO nEO average compensation actually paid amount year over year change percent.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="cmcsa_NonPEONEOAverageCompensationActuallyPaidAmountYearOverYearChangePercent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Average Compensation "Actually Paid" to non-PEOs, YOY CHANGE</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="cmcsa_NetIncomeLossYearOverYearChangePercent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Net Income Loss Year Over Year Change Percent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="cmcsa_NetIncomeLossYearOverYearChangePercent_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">net income loss year over year change percent.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="cmcsa_NetIncomeLossYearOverYearChangePercent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net Income, YOY CHANGE</link:label>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_AmendmentFlag" xlink:to="dei_AmendmentFlag_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="cmcsa_TotalShareholderReturnAmountYearOverYearChangePercent" xlink:to="cmcsa_TotalShareholderReturnAmountYearOverYearChangePercent_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_DocumentType" xlink:to="dei_DocumentType_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityCentralIndexKey" xlink:to="dei_EntityCentralIndexKey_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="cmcsa_ProfitLossYearOverYearChangePercent" xlink:to="cmcsa_ProfitLossYearOverYearChangePercent_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ProfitLoss" xlink:to="us-gaap_ProfitLoss_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="cmcsa_PEOActuallyPaidCompensationAmountYearOverYearChangePercent" xlink:to="cmcsa_PEOActuallyPaidCompensationAmountYearOverYearChangePercent_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="cmcsa_PeerGroupTotalShareholderReturnAmountYearOverYearChangePercent" xlink:to="cmcsa_PeerGroupTotalShareholderReturnAmountYearOverYearChangePercent_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_CoverAbstract" xlink:to="dei_CoverAbstract_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="cmcsa_LessFairValueOfAwardsForfeitedDuringTheCoveredYearMember" xlink:to="cmcsa_LessFairValueOfAwardsForfeitedDuringTheCoveredYearMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="cmcsa_CompanySelectedMeasureAmountYearOverYearChangePercent" xlink:to="cmcsa_CompanySelectedMeasureAmountYearOverYearChangePercent_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityRegistrantName" xlink:to="dei_EntityRegistrantName_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="cmcsa_NonPEONEOAverageCompensationActuallyPaidAmountYearOverYearChangePercent" xlink:to="cmcsa_NonPEONEOAverageCompensationActuallyPaidAmountYearOverYearChangePercent_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="cmcsa_NetIncomeLossYearOverYearChangePercent" xlink:to="cmcsa_NetIncomeLossYearOverYearChangePercent_lbl"/>
        </link:labelLink>
        <link:presentationLink xlink:role="http://comcastcorp.com/20260424/taxonomy/role/DocumentDocumentAndEntityInformation" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_CoverAbstract" xlink:label="dei_CoverAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentType" xlink:label="dei_DocumentType"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityRegistrantName" xlink:label="dei_EntityRegistrantName"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityCentralIndexKey" xlink:label="dei_EntityCentralIndexKey"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_AmendmentFlag" xlink:label="dei_AmendmentFlag"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="dei_CoverAbstract" xlink:to="dei_DocumentType" order="49.0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="dei_CoverAbstract" xlink:to="dei_EntityRegistrantName" order="50.0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="dei_CoverAbstract" xlink:to="dei_EntityCentralIndexKey" order="51.0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="dei_CoverAbstract" xlink:to="dei_AmendmentFlag" order="52.0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://xbrl.sec.gov/ecd/role/PvpDisclosure" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_AllAdjToCompMember" xlink:label="ecd_AllAdjToCompMember"/>
          <link:loc xlink:type="locator" xlink:href="cmcsa-20260424.xsd#cmcsa_LessFairValueOfAwardsForfeitedDuringTheCoveredYearMember" xlink:label="cmcsa_LessFairValueOfAwardsForfeitedDuringTheCoveredYearMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_PayVsPerformanceDisclosureLineItems" xlink:label="ecd_PayVsPerformanceDisclosureLineItems"/>
          <link:loc xlink:type="locator" xlink:href="cmcsa-20260424.xsd#cmcsa_PEOActuallyPaidCompensationAmountYearOverYearChangePercent" xlink:label="cmcsa_PEOActuallyPaidCompensationAmountYearOverYearChangePercent"/>
          <link:loc xlink:type="locator" xlink:href="cmcsa-20260424.xsd#cmcsa_NonPEONEOAverageCompensationActuallyPaidAmountYearOverYearChangePercent" xlink:label="cmcsa_NonPEONEOAverageCompensationActuallyPaidAmountYearOverYearChangePercent"/>
          <link:loc xlink:type="locator" xlink:href="cmcsa-20260424.xsd#cmcsa_NetIncomeLossYearOverYearChangePercent" xlink:label="cmcsa_NetIncomeLossYearOverYearChangePercent"/>
          <link:loc xlink:type="locator" xlink:href="cmcsa-20260424.xsd#cmcsa_ProfitLossYearOverYearChangePercent" xlink:label="cmcsa_ProfitLossYearOverYearChangePercent"/>
          <link:loc xlink:type="locator" xlink:href="cmcsa-20260424.xsd#cmcsa_CompanySelectedMeasureAmountYearOverYearChangePercent" xlink:label="cmcsa_CompanySelectedMeasureAmountYearOverYearChangePercent"/>
          <link:loc xlink:type="locator" xlink:href="cmcsa-20260424.xsd#cmcsa_TotalShareholderReturnAmountYearOverYearChangePercent" xlink:label="cmcsa_TotalShareholderReturnAmountYearOverYearChangePercent"/>
          <link:loc xlink:type="locator" xlink:href="cmcsa-20260424.xsd#cmcsa_PeerGroupTotalShareholderReturnAmountYearOverYearChangePercent" xlink:label="cmcsa_PeerGroupTotalShareholderReturnAmountYearOverYearChangePercent"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProfitLoss" xlink:label="us-gaap_ProfitLoss"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="ecd_AllAdjToCompMember" xlink:to="cmcsa_LessFairValueOfAwardsForfeitedDuringTheCoveredYearMember" order="4.0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="ecd_PayVsPerformanceDisclosureLineItems" xlink:to="cmcsa_PEOActuallyPaidCompensationAmountYearOverYearChangePercent" order="32.0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="ecd_PayVsPerformanceDisclosureLineItems" xlink:to="cmcsa_NonPEONEOAverageCompensationActuallyPaidAmountYearOverYearChangePercent" order="33.0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="ecd_PayVsPerformanceDisclosureLineItems" xlink:to="cmcsa_NetIncomeLossYearOverYearChangePercent" order="34.0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="ecd_PayVsPerformanceDisclosureLineItems" xlink:to="cmcsa_ProfitLossYearOverYearChangePercent" order="35.0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="ecd_PayVsPerformanceDisclosureLineItems" xlink:to="cmcsa_CompanySelectedMeasureAmountYearOverYearChangePercent" order="36.0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="ecd_PayVsPerformanceDisclosureLineItems" xlink:to="cmcsa_TotalShareholderReturnAmountYearOverYearChangePercent" order="37.0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="ecd_PayVsPerformanceDisclosureLineItems" xlink:to="cmcsa_PeerGroupTotalShareholderReturnAmountYearOverYearChangePercent" order="38.0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="ecd_PayVsPerformanceDisclosureLineItems" xlink:to="us-gaap_ProfitLoss" order="39.0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
        </link:presentationLink>
        <link:definitionLink xlink:type="extended" xlink:role="http://xbrl.sec.gov/ecd/role/PvpAdjustmentsOnly">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_AllAdjToCompMember" xlink:label="ecd_AllAdjToCompMember"/>
          <link:loc xlink:type="locator" xlink:href="cmcsa-20260424.xsd#cmcsa_LessFairValueOfAwardsForfeitedDuringTheCoveredYearMember" xlink:label="cmcsa_LessFairValueOfAwardsForfeitedDuringTheCoveredYearMember"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ecd_AllAdjToCompMember" xlink:to="cmcsa_LessFairValueOfAwardsForfeitedDuringTheCoveredYearMember" priority="2" use="optional"/>
        </link:definitionLink>
      </link:linkbase>
    </xsd:appinfo>
  </xsd:annotation>
  <xsd:element id="cmcsa_NetIncomeLossYearOverYearChangePercent" name="NetIncomeLossYearOverYearChangePercent" type="xbrli:pureItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="cmcsa_PEOActuallyPaidCompensationAmountYearOverYearChangePercent" name="PEOActuallyPaidCompensationAmountYearOverYearChangePercent" type="xbrli:pureItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="cmcsa_CompanySelectedMeasureAmountYearOverYearChangePercent" name="CompanySelectedMeasureAmountYearOverYearChangePercent" type="xbrli:pureItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="cmcsa_NonPEONEOAverageCompensationActuallyPaidAmountYearOverYearChangePercent" name="NonPEONEOAverageCompensationActuallyPaidAmountYearOverYearChangePercent" type="xbrli:pureItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="cmcsa_ProfitLossYearOverYearChangePercent" name="ProfitLossYearOverYearChangePercent" type="xbrli:pureItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="cmcsa_TotalShareholderReturnAmountYearOverYearChangePercent" name="TotalShareholderReturnAmountYearOverYearChangePercent" type="xbrli:pureItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="cmcsa_PeerGroupTotalShareholderReturnAmountYearOverYearChangePercent" name="PeerGroupTotalShareholderReturnAmountYearOverYearChangePercent" type="xbrli:pureItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="cmcsa_LessFairValueOfAwardsForfeitedDuringTheCoveredYearMember" name="LessFairValueOfAwardsForfeitedDuringTheCoveredYearMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
</xsd:schema>
