content: <?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>675 BERING DRIVE</com:street1>
          <com:street2>SUITE 400</com:street2>
          <com:city>HOUSTON</com:city>
          <com:stateOrCountry>TX</com:stateOrCountry>
          <com:zipCode>77057</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>30000</noOfUnitsSold>
        <aggregateMarketValue>5550600.00</aggregateMarketValue>
        <noOfUnitsOutstanding>35769739</noOfUnitsOutstanding>
        <approxSaleDate>08/31/2023</approxSaleDate>
        <securitiesExchangeName>NYSE</securitiesExchangeName>
      </securitiesInformation>
      <securitiesToBeSold>
        <securitiesClassTitle>Common</securitiesClassTitle>
        <acquiredDate>05/23/2023</acquiredDate>
        <natureOfAcquisitionTransaction>Stock Award</natureOfAcquisitionTransaction>
        <nameOfPersonfromWhomAcquired>Issuer</nameOfPersonfromWhomAcquired>
        <isGiftTransaction>N</isGiftTransaction>
        <amountOfSecuritiesAcquired>1159</amountOfSecuritiesAcquired>
        <paymentDate>05/23/2023</paymentDate>
        <natureOfPayment>Compensation</natureOfPayment>
      </securitiesToBeSold>
      <securitiesToBeSold>
        <securitiesClassTitle>Common</securitiesClassTitle>
        <acquiredDate>09/06/2019</acquiredDate>
        <natureOfAcquisitionTransaction>Purchase</natureOfAcquisitionTransaction>
        <nameOfPersonfromWhomAcquired>Open Market</nameOfPersonfromWhomAcquired>
        <isGiftTransaction>N</isGiftTransaction>
        <amountOfSecuritiesAcquired>5000</amountOfSecuritiesAcquired>
        <paymentDate>09/06/2019</paymentDate>
        <natureOfPayment>Cash/ check</natureOfPayment>
      </securitiesToBeSold>
      <securitiesToBeSold>
        <securitiesClassTitle>Common</securitiesClassTitle>
        <acquiredDate>08/01/2019</acquiredDate>
        <natureOfAcquisitionTransaction>Purchase</natureOfAcquisitionTransaction>
        <nameOfPersonfromWhomAcquired>Open Market</nameOfPersonfromWhomAcquired>
        <isGiftTransaction>N</isGiftTransaction>
        <amountOfSecuritiesAcquired>5089</amountOfSecuritiesAcquired>
        <paymentDate>08/01/2019</paymentDate>
        <natureOfPayment>Cash/ check</natureOfPayment>
      </securitiesToBeSold>
      <securitiesToBeSold>
        <securitiesClassTitle>Common</securitiesClassTitle>
        <acquiredDate>03/07/2018</acquiredDate>
        <natureOfAcquisitionTransaction>Purchase</natureOfAcquisitionTransaction>
        <nameOfPersonfromWhomAcquired>Open Market</nameOfPersonfromWhomAcquired>
        <isGiftTransaction>N</isGiftTransaction>
        <amountOfSecuritiesAcquired>2500</amountOfSecuritiesAcquired>
        <paymentDate>03/07/2018</paymentDate>
        <natureOfPayment>Cash/ check</natureOfPayment>
      </securitiesToBeSold>
      <securitiesToBeSold>
        <securitiesClassTitle>Common</securitiesClassTitle>
        <acquiredDate>02/27/2018</acquiredDate>
        <natureOfAcquisitionTransaction>Purchase</natureOfAcquisitionTransaction>
        <nameOfPersonfromWhomAcquired>Open Market</nameOfPersonfromWhomAcquired>
        <isGiftTransaction>N</isGiftTransaction>
        <amountOfSecuritiesAcquired>2500</amountOfSecuritiesAcquired>
        <paymentDate>02/27/2018</paymentDate>
        <natureOfPayment>Cash/ check</natureOfPayment>
      </securitiesToBeSold>
      <securitiesToBeSold>
        <securitiesClassTitle>Common</securitiesClassTitle>
        <acquiredDate>11/15/2017</acquiredDate>
        <natureOfAcquisitionTransaction>Purchase</natureOfAcquisitionTransaction>
        <nameOfPersonfromWhomAcquired>Open Market</nameOfPersonfromWhomAcquired>
        <isGiftTransaction>N</isGiftTransaction>
        <amountOfSecuritiesAcquired>2000</amountOfSecuritiesAcquired>
        <paymentDate>11/15/2017</paymentDate>
        <natureOfPayment>Cash/ check</natureOfPayment>
      </securitiesToBeSold>
      <securitiesToBeSold>
        <securitiesClassTitle>Common</securitiesClassTitle>
        <acquiredDate>11/14/2017</acquiredDate>
        <natureOfAcquisitionTransaction>Purchase</natureOfAcquisitionTransaction>
        <nameOfPersonfromWhomAcquired>Open Market</nameOfPersonfromWhomAcquired>
        <isGiftTransaction>N</isGiftTransaction>
        <amountOfSecuritiesAcquired>3000</amountOfSecuritiesAcquired>
        <paymentDate>11/14/2017</paymentDate>
        <natureOfPayment>Cash/ check</natureOfPayment>
      </securitiesToBeSold>
      <securitiesToBeSold>
        <securitiesClassTitle>Common</securitiesClassTitle>
        <acquiredDate>03/03/2017</acquiredDate>
        <natureOfAcquisitionTransaction>Purchase</natureOfAcquisitionTransaction>
        <nameOfPersonfromWhomAcquired>Open Market</nameOfPersonfromWhomAcquired>
        <isGiftTransaction>N</isGiftTransaction>
        <amountOfSecuritiesAcquired>3100</amountOfSecuritiesAcquired>
        <paymentDate>03/03/2017</paymentDate>
        <natureOfPayment>Cash/ check</natureOfPayment>
      </securitiesToBeSold>
      <securitiesToBeSold>
        <securitiesClassTitle>Common</securitiesClassTitle>
        <acquiredDate>03/07/2017</acquiredDate>
        <natureOfAcquisitionTransaction>Purchase</natureOfAcquisitionTransaction>
        <nameOfPersonfromWhomAcquired>Open Market</nameOfPersonfromWhomAcquired>
        <isGiftTransaction>N</isGiftTransaction>
        <amountOfSecuritiesAcquired>400</amountOfSecuritiesAcquired>
        <paymentDate>03/07/2017</paymentDate>
        <natureOfPayment>Cash/ check</natureOfPayment>
      </securitiesToBeSold>
      <securitiesToBeSold>
        <securitiesClassTitle>Common</securitiesClassTitle>
        <acquiredDate>03/06/2017</acquiredDate>
        <natureOfAcquisitionTransaction>Purchase</natureOfAcquisitionTransaction>
        <nameOfPersonfromWhomAcquired>Open Market</nameOfPersonfromWhomAcquired>
        <isGiftTransaction>N</isGiftTransaction>
        <amountOfSecuritiesAcquired>1500</amountOfSecuritiesAcquired>
        <paymentDate>03/06/2017</paymentDate>
        <natureOfPayment>Cash/ check</natureOfPayment>
      </securitiesToBeSold>
      <securitiesToBeSold>
        <securitiesClassTitle>Common</securitiesClassTitle>
        <acquiredDate>05/03/2017</acquiredDate>
        <natureOfAcquisitionTransaction>Purchase</natureOfAcquisitionTransaction>
        <nameOfPersonfromWhomAcquired>Open Market</nameOfPersonfromWhomAcquired>
        <isGiftTransaction>N</isGiftTransaction>
        <amountOfSecuritiesAcquired>3752</amountOfSecuritiesAcquired>
        <paymentDate>05/03/2017</paymentDate>
        <natureOfPayment>Cash/ check</natureOfPayment>
      </securitiesToBeSold>
      <nothingToReportFlagOnSecuritiesSoldInPast3Months>Y</nothingToReportFlagOnSecuritiesSoldInPast3Months>
      <noticeSignature>
        <noticeDate>08/31/2023</noticeDate>
        <signature>/s/ Cristina Garcia, as a duly authorized representative of Fidelity Brokerage Services LLC, as attorney-in-fact for MYERS FRANKLIN</signature>
      </noticeSignature>
    </formData>
  </edgarSubmission>
metadata_documents: [{"type": "144", "sequence": "1", "filename": "primary_doc.xml", "secsgml_size_bytes": 8119}]
text: 144
  0001207002
  XXXXXXXX
  LIVE
  0001035983
  COMFORT SYSTEMS USA INC
  001-13011
  675 BERING DRIVE
  SUITE 400
  HOUSTON
  TX
  77057
  7138309600
  MYERS FRANKLIN
  Director
  Common
  Fidelity Brokerage Services LLC
  245 Summer Street
  Boston
  MA
  02110
  30000
  5550600.00
  35769739
  08/31/2023
  NYSE
  Common
  05/23/2023
  Stock Award
  Issuer
  N
  1159
  05/23/2023
  Compensation
  Common
  09/06/2019
  Purchase
  Open Market
  N
  5000
  09/06/2019
  Cash/ check
  Common
  08/01/2019
  Purchase
  Open Market
  N
  5089
  08/01/2019
  Cash/ check
  Common
  03/07/2018
  Purchase
  Open Market
  N
  2500
  03/07/2018
  Cash/ check
  Common
  02/27/2018
  Purchase
  Open Market
  N
  2500
  02/27/2018
  Cash/ check
  Common
  11/15/2017
  Purchase
  Open Market
  N
  2000
  11/15/2017
  Cash/ check
  Common
  11/14/2017
  Purchase
  Open Market
  N
  3000
  11/14/2017
  Cash/ check
  Common
  03/03/2017
  Purchase
  Open Market
  N
  3100
  03/03/2017
  Cash/ check
  Common
  03/07/2017
  Purchase
  Open Market
  N
  400
  03/07/2017
  Cash/ check
  Common
  03/06/2017
  Purchase
  Open Market
  N
  1500
  03/06/2017
  Cash/ check
  Common
  05/03/2017
  Purchase
  Open Market
  N
  3752
  05/03/2017
  Cash/ check
  Y
  08/31/2023
  /s/ Cristina Garcia, as a duly authorized representative of Fidelity Brokerage Services LLC, as attorney-in-fact for MYERS FRANKLIN