<SEC-DOCUMENT>0001415889-24-030069.txt : 20241223
<SEC-HEADER>0001415889-24-030069.hdr.sgml : 20241223
<ACCEPTANCE-DATETIME>20241223161530
ACCESSION NUMBER:		0001415889-24-030069
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20241220
FILED AS OF DATE:		20241223
DATE AS OF CHANGE:		20241223

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			van der Horst Edward
		CENTRAL INDEX KEY:			0001957499
		ORGANIZATION NAME:           	

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-39980
		FILM NUMBER:		241573796

	MAIL ADDRESS:	
		STREET 1:		C/O SENSEI BIOTHERAPEUTICS, INC.
		STREET 2:		451 D STREET, SUITE 710
		CITY:			BOSTON
		STATE:			MA
		ZIP:			02210

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			Sensei Biotherapeutics, Inc.
		CENTRAL INDEX KEY:			0001829802
		STANDARD INDUSTRIAL CLASSIFICATION:	PHARMACEUTICAL PREPARATIONS [2834]
		ORGANIZATION NAME:           	03 Life Sciences
		IRS NUMBER:				000000000
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		1405 RESEARCH BLVD, SUITE 125
		CITY:			ROCKVILLE
		STATE:			MD
		ZIP:			20850
		BUSINESS PHONE:		(240) 243-8000

	MAIL ADDRESS:	
		STREET 1:		1405 RESEARCH BLVD, SUITE 125
		CITY:			ROCKVILLE
		STATE:			MD
		ZIP:			20850
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>form4-12232024_041227.xml
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0508</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2024-12-20</periodOfReport>

    <issuer>
        <issuerCik>0001829802</issuerCik>
        <issuerName>Sensei Biotherapeutics, Inc.</issuerName>
        <issuerTradingSymbol>SNSE</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001957499</rptOwnerCik>
            <rptOwnerName>van der Horst Edward</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O SENSEI BIOTHERAPEUTICS, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>1405 RESEARCH BLVD, SUITE 125</rptOwnerStreet2>
            <rptOwnerCity>ROCKVILLE</rptOwnerCity>
            <rptOwnerState>MD</rptOwnerState>
            <rptOwnerZipCode>20850</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>false</isDirector>
            <isOfficer>true</isOfficer>
            <isTenPercentOwner>false</isTenPercentOwner>
            <isOther>false</isOther>
            <officerTitle>CHIEF SCIENTIFIC OFFICER</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <aff10b5One>0</aff10b5One>

    <nonDerivativeTable></nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Stock Option (Right to Buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>0.4499</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2024-12-20</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>100000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <value>2034-12-19</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>100000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>100000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">100% of the shares subject to the option shall vest on December 1, 2025, subject to the Reporting Person's continuous service with the Issuer as of such date.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Mark Ballantyne, Attorney-in-Fact</signatureName>
        <signatureDate>2024-12-23</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>