<?xml version="1.0" encoding="UTF-8"?><edgarSubmission xmlns="http://www.sec.gov/edgar/ownership" xmlns:com="http://www.sec.gov/edgar/common">
  <headerData>
    <submissionType>144</submissionType>
    <filerInfo>
      <filer>
        <filerCredentials>
          <cik>0001207002</cik>
          <ccc>XXXXXXXX</ccc>
        </filerCredentials>
      </filer>
      <liveTestFlag>LIVE</liveTestFlag>



    </filerInfo>
  </headerData>
  <formData>
    <issuerInfo>
      <issuerCik>0001035983</issuerCik>
      <issuerName>COMFORT SYSTEMS USA INC</issuerName>
      <secFileNumber>001-13011</secFileNumber>
      <issuerAddress>
        <com:street1>9753 KATY FREEWAY</com:street1>
        <com:street2>SUITE 700</com:street2>
        <com:city>HOUSTON</com:city>
        <com:stateOrCountry>TX</com:stateOrCountry>
        <com:zipCode>77024</com:zipCode>
      </issuerAddress>
      <issuerContactPhone>7138309600</issuerContactPhone>
      <nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>MYERS FRANKLIN</nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>
      <relationshipsToIssuer>
        <relationshipToIssuer>Director</relationshipToIssuer>
      </relationshipsToIssuer>
    </issuerInfo>
    <securitiesInformation>
      <securitiesClassTitle>Common</securitiesClassTitle>
      <brokerOrMarketmakerDetails>
        <name>FIDELITY BROKERAGE SERVICES LLC</name>
        <address>
          <com:street1>245 Summer Street</com:street1>
          <com:city>BOSTON</com:city>
          <com:stateOrCountry>MA</com:stateOrCountry>
          <com:zipCode>02110</com:zipCode>
        </address>
      </brokerOrMarketmakerDetails>
      <noOfUnitsSold>3500</noOfUnitsSold>
      <aggregateMarketValue>5938345.00</aggregateMarketValue>
      <noOfUnitsOutstanding>35194329</noOfUnitsOutstanding>
      <approxSaleDate>08/10/2026</approxSaleDate>
      <securitiesExchangeName>NYSE</securitiesExchangeName>
    </securitiesInformation>
    <securitiesToBeSold>
      <securitiesClassTitle>Common</securitiesClassTitle>
      <acquiredDate>09/11/2015</acquiredDate>
      <natureOfAcquisitionTransaction>OPEN MKT PURCHASE</natureOfAcquisitionTransaction>
      <nameOfPersonfromWhomAcquired>ISSUER</nameOfPersonfromWhomAcquired>
      <isGiftTransaction>N</isGiftTransaction>
      <amountOfSecuritiesAcquired>3500</amountOfSecuritiesAcquired>
      <paymentDate>09/11/2015</paymentDate>
      <natureOfPayment>Cash/Check</natureOfPayment>
    </securitiesToBeSold>
    <nothingToReportFlagOnSecuritiesSoldInPast3Months>Y</nothingToReportFlagOnSecuritiesSoldInPast3Months>
    <noticeSignature>
      <noticeDate>08/10/2026</noticeDate>
      <signature>/s/ Jordyn Davis as a duly authorized representative of Fidelity Brokerage Services LLC, as attorney-in-fact for MYERS FRANKLIN</signature>
    </noticeSignature>
  </formData>
</edgarSubmission>
