<SEC-DOCUMENT>0000866273-21-000016.txt : 20210405
<SEC-HEADER>0000866273-21-000016.hdr.sgml : 20210405
<ACCEPTANCE-DATETIME>20210405141519
ACCESSION NUMBER:		0000866273-21-000016
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20210401
FILED AS OF DATE:		20210405
DATE AS OF CHANGE:		20210405

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			MILLER JAMES HARRY
		CENTRAL INDEX KEY:			0001608365

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-15461
		FILM NUMBER:		21804828

	MAIL ADDRESS:	
		STREET 1:		5100 EAST SKELLY DRIVE
		STREET 2:		SUITE 700
		CITY:			TULSA
		STATE:			OK
		ZIP:			74135

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			MATRIX SERVICE CO
		CENTRAL INDEX KEY:			0000866273
		STANDARD INDUSTRIAL CLASSIFICATION:	CONSTRUCTION SPECIAL TRADE CONTRACTORS [1700]
		IRS NUMBER:				731352174
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			0630

	BUSINESS ADDRESS:	
		STREET 1:		5100 EAST SKELLY DRIVE
		STREET 2:		SUITE 500
		CITY:			TULSA
		STATE:			OK
		ZIP:			74135
		BUSINESS PHONE:		9188388822

	MAIL ADDRESS:	
		STREET 1:		5100 EAST SKELLY DRIVE
		STREET 2:		SUITE 500
		CITY:			TULSA
		STATE:			OK
		ZIP:			74135
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>wf-form4_161764646457969.xml
<DESCRIPTION>FORM 4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2021-04-01</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000866273</issuerCik>
        <issuerName>MATRIX SERVICE CO</issuerName>
        <issuerTradingSymbol>MTRX</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001608365</rptOwnerCik>
            <rptOwnerName>MILLER JAMES HARRY</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>5100 EAST SKELLY DRIVE</rptOwnerStreet1>
            <rptOwnerStreet2>SUITE 100</rptOwnerStreet2>
            <rptOwnerCity>TULSA</rptOwnerCity>
            <rptOwnerState>OK</rptOwnerState>
            <rptOwnerZipCode>74135</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>COMMON STOCK</value>
                <footnoteId id="F1"/>
            </securityTitle>
            <transactionDate>
                <value>2021-04-01</value>
                <footnoteId id="F2"/>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>5</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionTimeliness>
                <value>E</value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>730</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>13.69</value>
                    <footnoteId id="F3"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>42359</value>
                    <footnoteId id="F4"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">MATRIX SERVICE COMPANY COMMON STOCK PURCHASED VIA THE MATRIX SERVICE COMPANY 2011 EMPLOYEE STOCK PURCHASE PLAN (&quot;THE ESPP&quot;) IN A TRANSACTION THAT WAS EXEMPT UNDER BOTH RULE 16b-3(c) AND RULE 16b-3(d) AND IS VOLUNTARILY REPORTED.</footnote>
        <footnote id="F2">SHARES WERE PURCHASED VIA THE ESPP. THE OFFERING PERIOD CONSISTED OF THE THREE MONTHS ENDED MARCH 31, 2021. THE SHARES WERE ACQUIRED ON THE FIRST DAY AFTER THE END OF THE OFFERING PERIOD.</footnote>
        <footnote id="F3">PER THE ESPP, THE PURCHASE PRICE WAS DETERMINED BY THE LAST CLOSING CONSOLIDATED BID PRICE PER SHARE ON THE PURCHASE DATE.</footnote>
        <footnote id="F4">INCLUDES 34,148 SHARES OF MATRIX SERVICE COMPANY COMMON STOCK OWNED OUTRIGHT.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>James H. Miller</signatureName>
        <signatureDate>2021-04-05</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
