<SEC-DOCUMENT>0001567619-22-021705.txt : 20221216
<SEC-HEADER>0001567619-22-021705.hdr.sgml : 20221216
<ACCEPTANCE-DATETIME>20221216160542
ACCESSION NUMBER:		0001567619-22-021705
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20221214
FILED AS OF DATE:		20221216
DATE AS OF CHANGE:		20221216

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			WEST ALFRED P JR
		CENTRAL INDEX KEY:			0001059374

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-10200
		FILM NUMBER:		221467978

	MAIL ADDRESS:	
		STREET 1:		1 FREEDOM VALLEY DRIVE
		CITY:			OAKS
		STATE:			PA
		ZIP:			19456

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			SEI INVESTMENTS CO
		CENTRAL INDEX KEY:			0000350894
		STANDARD INDUSTRIAL CLASSIFICATION:	SECURITY BROKERS, DEALERS & FLOTATION COMPANIES [6211]
		IRS NUMBER:				231707341
		STATE OF INCORPORATION:			PA
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		1 FREEDOM VALLEY DRIVE
		CITY:			OAKS
		STATE:			PA
		ZIP:			19456-1100
		BUSINESS PHONE:		6106761000

	MAIL ADDRESS:	
		STREET 1:		1 FREEDOM VALLEY DRIVE
		CITY:			OAKS
		STATE:			PA
		ZIP:			19456-1100

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	SEI INVESTMENT CO
		DATE OF NAME CHANGE:	20040806

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	SEI CORP
		DATE OF NAME CHANGE:	19920703
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>doc1.xml
<DESCRIPTION>FORM 4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2022-12-14</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000350894</issuerCik>
        <issuerName>SEI INVESTMENTS CO</issuerName>
        <issuerTradingSymbol>SEIC</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001059374</rptOwnerCik>
            <rptOwnerName>WEST ALFRED P JR</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>1 FREEDOM VALLLEY DRIVE</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>OAKS</rptOwnerCity>
            <rptOwnerState>PA</rptOwnerState>
            <rptOwnerZipCode>19456</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Executive Chairman</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2022-12-14</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>35368</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>60.68</value>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>9076424</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2022-12-15</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>27800</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>59.27</value>
                    <footnoteId id="F2"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>9048624</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2022-12-15</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>200</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>60.06</value>
                    <footnoteId id="F3"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>9048424</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">Represents the weighted average of a range of sale prices from $60.27 to $61.07. The reporting person undertakes to provide to the Staff of the Securities and Exchange Commission, the Company or any stockholder of the Company, upon request, full information regarding the number of shares sold at each separate price.</footnote>
        <footnote id="F2">Represents the weighted average of a range of sale prices from $58.96 to $59.89. The reporting person undertakes to provide to the Staff of the Securities and Exchange Commission, the Company or any stockholder of the Company, upon request, full information regarding the number of shares sold at each separate price.</footnote>
        <footnote id="F3">Represents the weighted average of a range of sale prices from $60.04 to $60.13. The reporting person undertakes to provide to the Staff of the Securities and Exchange Commission, the Company or any stockholder of the Company, upon request, full information regarding the number of shares sold at each separate price.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Alfred P. West, Jr., by Michael N. Peterson, attorney in fact</signatureName>
        <signatureDate>2022-12-16</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
