<SEC-DOCUMENT>0000831641-23-000085.txt : 20231122
<SEC-HEADER>0000831641-23-000085.hdr.sgml : 20231122
<ACCEPTANCE-DATETIME>20231122194723
ACCESSION NUMBER:		0000831641-23-000085
CONFORMED SUBMISSION TYPE:	4/A
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20231118
FILED AS OF DATE:		20231122
DATE AS OF CHANGE:		20231122

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Volpi Kirsten M
		CENTRAL INDEX KEY:			0001582882

	FILING VALUES:
		FORM TYPE:		4/A
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-19655
		FILM NUMBER:		231434801

	MAIL ADDRESS:	
		STREET 1:		TETRA TECH, INC.
		STREET 2:		3475 EAST FOOTHILL BOULEVARD
		CITY:			PASADENA
		STATE:			CA
		ZIP:			91107

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			TETRA TECH INC
		CENTRAL INDEX KEY:			0000831641
		STANDARD INDUSTRIAL CLASSIFICATION:	SERVICES-ENGINEERING SERVICES [8711]
		IRS NUMBER:				954148514
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1001

	BUSINESS ADDRESS:	
		STREET 1:		3475 EAST FOOTHILL BOULEVARD
		CITY:			PASADENA
		STATE:			CA
		ZIP:			91107
		BUSINESS PHONE:		6263514664

	MAIL ADDRESS:	
		STREET 1:		3475 EAST FOOTHILL BOULEVARD
		CITY:			PASADENA
		STATE:			CA
		ZIP:			91107
</SEC-HEADER>
<DOCUMENT>
<TYPE>4/A
<SEQUENCE>1
<FILENAME>wk-form4a_1700700432.xml
<DESCRIPTION>FORM 4/A
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0508</schemaVersion>

    <documentType>4/A</documentType>

    <periodOfReport>2023-11-18</periodOfReport>

    <dateOfOriginalSubmission>2023-11-21</dateOfOriginalSubmission>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000831641</issuerCik>
        <issuerName>TETRA TECH INC</issuerName>
        <issuerTradingSymbol>TTEK</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001582882</rptOwnerCik>
            <rptOwnerName>Volpi Kirsten M</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>3475 EAST FOOTHILL BOULEVARD</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>PASADENA</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>91107</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <aff10b5One>0</aff10b5One>

    <nonDerivativeTable>
        <nonDerivativeHolding>
            <securityTitle>
                <value>COMMON STOCK</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>14388</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">On the Reporting Person's Form 4 filed 11/21/23, 200 shares were reported sold twice in error in Table I. Balance reported reflects an adjustment to the correct amount beneficially owned.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Preston Hopson, Attorney-in-fact for Kirsten M. Volpi</signatureName>
        <signatureDate>2023-11-22</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
