<SEC-DOCUMENT>0000932471-25-000377.txt : 20250407
<SEC-HEADER>0000932471-25-000377.hdr.sgml : 20250407
<ACCEPTANCE-DATETIME>20250407115133
ACCESSION NUMBER:		0000932471-25-000377
CONFORMED SUBMISSION TYPE:	SCHEDULE 13G/A
PUBLIC DOCUMENT COUNT:		1
FILED AS OF DATE:		20250407
DATE AS OF CHANGE:		20250407

SUBJECT COMPANY:	

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			TETRA TECH INC
		CENTRAL INDEX KEY:			0000831641
		STANDARD INDUSTRIAL CLASSIFICATION:	SERVICES-ENGINEERING SERVICES [8711]
		ORGANIZATION NAME:           	07 Trade & Services
		EIN:				954148514
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			0928

	FILING VALUES:
		FORM TYPE:		SCHEDULE 13G/A
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	005-43035
		FILM NUMBER:		25816980

	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

FILED BY:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			VANGUARD GROUP INC
		CENTRAL INDEX KEY:			0000102909
		ORGANIZATION NAME:           	
		EIN:				231945930
		STATE OF INCORPORATION:			PA
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		SCHEDULE 13G/A

	BUSINESS ADDRESS:	
		STREET 1:		100 VANGUARD BLVD
		CITY:			MALVERN
		STATE:			PA
		ZIP:			19355
		BUSINESS PHONE:		6106691000

	MAIL ADDRESS:	
		STREET 1:		PO BOX 2600
		STREET 2:		V26
		CITY:			VALLEY FORGE
		STATE:			PA
		ZIP:			19482-2600
</SEC-HEADER>
<DOCUMENT>
<TYPE>SCHEDULE 13G/A
<SEQUENCE>1
<FILENAME>primary_doc.xml
<TEXT>
<XML>
<?xml version="1.0" encoding="UTF-8"?><edgarSubmission xmlns="http://www.sec.gov/edgar/schedule13g" xmlns:com="http://www.sec.gov/edgar/common">
<headerData>
<submissionType>SCHEDULE 13G/A</submissionType>
<filerInfo>
<filer>
<filerCredentials>
<cik>0000102909</cik>
<ccc>XXXXXXXX</ccc>
</filerCredentials>
</filer>
<liveTestFlag>LIVE</liveTestFlag>
</filerInfo>
</headerData>
<formData>
<coverPageHeader>
<amendmentNo>15</amendmentNo>
<securitiesClassTitle>Common Stock</securitiesClassTitle>
<eventDateRequiresFilingThisStatement>03/31/2025</eventDateRequiresFilingThisStatement>
<issuerInfo>
<issuerCik>0000831641</issuerCik>
<issuerName>Tetra Tech Inc</issuerName>
<issuerCusip>88162G103</issuerCusip>
<issuerPrincipalExecutiveOfficeAddress>
<com:street1>3475 East Foothill Blvd</com:street1>
<com:city>Pasadena</com:city>
<com:stateOrCountry>CA</com:stateOrCountry>
<com:zipCode>91107</com:zipCode>
</issuerPrincipalExecutiveOfficeAddress>
</issuerInfo>
<designateRulesPursuantThisScheduleFiled>
<designateRulePursuantThisScheduleFiled>Rule 13d-1(b)</designateRulePursuantThisScheduleFiled>
</designateRulesPursuantThisScheduleFiled>
</coverPageHeader>
<coverPageHeaderReportingPersonDetails>
<reportingPersonName>The Vanguard Group</reportingPersonName>
<citizenshipOrOrganization>PA</citizenshipOrOrganization>
<reportingPersonBeneficiallyOwnedNumberOfShares>
<soleVotingPower>0</soleVotingPower>
<sharedVotingPower>103963</sharedVotingPower>
<soleDispositivePower>26793343</soleDispositivePower>
<sharedDispositivePower>392452</sharedDispositivePower>
</reportingPersonBeneficiallyOwnedNumberOfShares>
<reportingPersonBeneficiallyOwnedAggregateNumberOfShares>27185795</reportingPersonBeneficiallyOwnedAggregateNumberOfShares>
<classPercent>10.14</classPercent>
<typeOfReportingPerson>IA</typeOfReportingPerson>
</coverPageHeaderReportingPersonDetails>
<items>
<item1>
<issuerName>Tetra Tech Inc</issuerName>
<issuerPrincipalExecutiveOfficeAddress>3475 East Foothill Blvd, Pasadena, CA, 91107</issuerPrincipalExecutiveOfficeAddress>
</item1>
<item2>
<filingPersonName>The Vanguard Group</filingPersonName>
<principalBusinessOfficeOrResidenceAddress>100 Vanguard Blvd., Malvern, PA 19355</principalBusinessOfficeOrResidenceAddress>
<citizenship>PA</citizenship>
</item2>
<item3>
<notApplicableFlag>N</notApplicableFlag>
<typeOfPersonFiling>IA</typeOfPersonFiling>
</item3>
<item4>
<amountBeneficiallyOwned>27185795</amountBeneficiallyOwned>
<classPercent>10.14</classPercent>
<numberOfSharesPersonHas>
<solePowerOrDirectToVote>0</solePowerOrDirectToVote>
<sharedPowerOrDirectToVote>103963</sharedPowerOrDirectToVote>
<solePowerOrDirectToDispose>26793343</solePowerOrDirectToDispose>
<sharedPowerOrDirectToDispose>392452</sharedPowerOrDirectToDispose>
</numberOfSharesPersonHas>
</item4>
<item5>
<notApplicableFlag>Y</notApplicableFlag>
</item5>
<item6>
<notApplicableFlag>N</notApplicableFlag>
<ownershipMoreThan5PercentOnBehalfOfAnotherPerson>The Vanguard Group, Inc.'s clients, including investment companies registered under the Investment Company Act of 1940 and other managed accounts, have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, the securities reported herein.

No one other person's interest in the securities reported herein is more than 5%.</ownershipMoreThan5PercentOnBehalfOfAnotherPerson>
</item6>
<item7>
<notApplicableFlag>Y</notApplicableFlag>
</item7>
<item8>
<notApplicableFlag>Y</notApplicableFlag>
</item8>
<item9>
<notApplicableFlag>Y</notApplicableFlag>
</item9>
<item10>
<notApplicableFlag>N</notApplicableFlag>
<certifications>By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under &amp;#167; 240.14a-11.</certifications>
</item10>
</items>
<signatureInformation>
<reportingPersonName>The Vanguard Group</reportingPersonName>
<signatureDetails>
<signature>Ashley Grim</signature>
<title>Head of Global Fund Administration</title>
<date>04/07/2025</date>
</signatureDetails>
</signatureInformation>
</formData>
</edgarSubmission>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
