content: <?xml version="1.0" encoding="UTF-8"?><edgarSubmission xmlns="http://www.sec.gov/edgar/ownership" xmlns:com="http://www.sec.gov/edgar/common">
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    <headerData>
      <submissionType>144</submissionType>
      <filerInfo>
        <filer>
          <filerCredentials>
            <cik>0001059374</cik>
            <ccc>XXXXXXXX</ccc>
          </filerCredentials>
        </filer>
        <liveTestFlag>LIVE</liveTestFlag>
  
  
  
      </filerInfo>
    </headerData>
    <formData>
      <issuerInfo>
        <issuerCik>0000350894</issuerCik>
        <issuerName>SEI Investments Co</issuerName>
        <secFileNumber>000-10200</secFileNumber>
        <issuerAddress>
          <com:street1>One Freedom Valley Drive</com:street1>
          <com:city>Oaks</com:city>
          <com:stateOrCountry>PA</com:stateOrCountry>
          <com:zipCode>19456-100</com:zipCode>
        </issuerAddress>
        <issuerContactPhone>610-676-1000</issuerContactPhone>
        <nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>Alfred Paul West Jr</nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>
        <relationshipsToIssuer>
          <relationshipToIssuer>Affiliate</relationshipToIssuer>
        </relationshipsToIssuer>
      </issuerInfo>
      <securitiesInformation>
        <securitiesClassTitle>Common</securitiesClassTitle>
        <brokerOrMarketmakerDetails>
          <name>J.P. Morgan Securities LLC</name>
          <address>
            <com:street1>390 Madison Avenue</com:street1>
            <com:street2>6th Floor</com:street2>
            <com:city>New York</com:city>
            <com:stateOrCountry>NY</com:stateOrCountry>
            <com:zipCode>10017</com:zipCode>
          </address>
        </brokerOrMarketmakerDetails>
        <noOfUnitsSold>213000</noOfUnitsSold>
        <aggregateMarketValue>12556350</aggregateMarketValue>
        <noOfUnitsOutstanding>133306087</noOfUnitsOutstanding>
        <approxSaleDate>06/20/2023</approxSaleDate>
        <securitiesExchangeName>Nasdaq</securitiesExchangeName>
      </securitiesInformation>
      <securitiesToBeSold>
        <securitiesClassTitle>Common</securitiesClassTitle>
        <acquiredDate>11/01/2019</acquiredDate>
        <natureOfAcquisitionTransaction>Private Transaction</natureOfAcquisitionTransaction>
        <nameOfPersonfromWhomAcquired>Issuer</nameOfPersonfromWhomAcquired>
        <isGiftTransaction>N</isGiftTransaction>
        <amountOfSecuritiesAcquired>300948</amountOfSecuritiesAcquired>
        <paymentDate>11/01/2019</paymentDate>
        <natureOfPayment>n/a</natureOfPayment>
      </securitiesToBeSold>
      <nothingToReportFlagOnSecuritiesSoldInPast3Months>N</nothingToReportFlagOnSecuritiesSoldInPast3Months>
      <securitiesSoldInPast3Months>
        <sellerDetails>
          <name>Alfred P West Jr</name>
          <address>
            <com:street1>Care of SEI Investments Co</com:street1>
            <com:street2>1 Freedom Valley Drive</com:street2>
            <com:city>Oaks</com:city>
            <com:stateOrCountry>PA</com:stateOrCountry>
            <com:zipCode>19456-1100</com:zipCode>
          </address>
        </sellerDetails>
        <securitiesClassTitle>Common</securitiesClassTitle>
        <saleDate>03/23/2023</saleDate>
        <amountOfSecuritiesSold>36462</amountOfSecuritiesSold>
        <grossProceeds>2020013.03</grossProceeds>
      </securitiesSoldInPast3Months>
      <securitiesSoldInPast3Months>
        <sellerDetails>
          <name>Alfred P West Jr</name>
          <address>
            <com:street1>Care of SEI Investments Co</com:street1>
            <com:street2>1 Freedom Valley Drive</com:street2>
            <com:city>Oaks</com:city>
            <com:stateOrCountry>PA</com:stateOrCountry>
            <com:zipCode>19456-1100</com:zipCode>
          </address>
        </sellerDetails>
        <securitiesClassTitle>Common</securitiesClassTitle>
        <saleDate>03/24/2023</saleDate>
        <amountOfSecuritiesSold>100000</amountOfSecuritiesSold>
        <grossProceeds>5459210</grossProceeds>
      </securitiesSoldInPast3Months>
      <securitiesSoldInPast3Months>
        <sellerDetails>
          <name>Alfred P West Jr</name>
          <address>
            <com:street1>Care of SEI Investments Co</com:street1>
            <com:street2>1 Freedom Valley Drive</com:street2>
            <com:city>Oaks</com:city>
            <com:stateOrCountry>PA</com:stateOrCountry>
            <com:zipCode>19456-1100</com:zipCode>
          </address>
        </sellerDetails>
        <securitiesClassTitle>Common</securitiesClassTitle>
        <saleDate>03/27/2023</saleDate>
        <amountOfSecuritiesSold>65900</amountOfSecuritiesSold>
        <grossProceeds>3653963.89</grossProceeds>
      </securitiesSoldInPast3Months>
      <securitiesSoldInPast3Months>
        <sellerDetails>
          <name>Alfred P West Jr</name>
          <address>
            <com:street1>Care of SEI Investments Co</com:street1>
            <com:street2>1 Freedom Valley Drive</com:street2>
            <com:city>Oaks</com:city>
            <com:stateOrCountry>PA</com:stateOrCountry>
            <com:zipCode>19456-1100</com:zipCode>
          </address>
        </sellerDetails>
        <securitiesClassTitle>Common</securitiesClassTitle>
        <saleDate>03/29/2023</saleDate>
        <amountOfSecuritiesSold>15659</amountOfSecuritiesSold>
        <grossProceeds>877841.97</grossProceeds>
      </securitiesSoldInPast3Months>
      <noticeSignature>
        <noticeDate>06/20/2023</noticeDate>
        <signature>J.P. Morgan Securities LLC as agent and attorney-in-fact for Alfred P West Jr</signature>
      </noticeSignature>
    </formData>
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text: 144
  0001059374
  XXXXXXXX
  LIVE
  0000350894
  SEI Investments Co
  000-10200
  One Freedom Valley Drive
  Oaks
  PA
  19456-100
  610-676-1000
  Alfred Paul West Jr
  Affiliate
  Common
  J.P. Morgan Securities LLC
  390 Madison Avenue
  6th Floor
  New York
  NY
  10017
  213000
  12556350
  133306087
  06/20/2023
  Nasdaq
  Common
  11/01/2019
  Private Transaction
  Issuer
  N
  300948
  11/01/2019
  n/a
  N
  Alfred P West Jr
  Care of SEI Investments Co
  1 Freedom Valley Drive
  Oaks
  PA
  19456-1100
  Common
  03/23/2023
  36462
  2020013.03
  Alfred P West Jr
  Care of SEI Investments Co
  1 Freedom Valley Drive
  Oaks
  PA
  19456-1100
  Common
  03/24/2023
  100000
  5459210
  Alfred P West Jr
  Care of SEI Investments Co
  1 Freedom Valley Drive
  Oaks
  PA
  19456-1100
  Common
  03/27/2023
  65900
  3653963.89
  Alfred P West Jr
  Care of SEI Investments Co
  1 Freedom Valley Drive
  Oaks
  PA
  19456-1100
  Common
  03/29/2023
  15659
  877841.97
  06/20/2023
  J.P. Morgan Securities LLC as agent and attorney-in-fact for Alfred P West Jr