<SEC-DOCUMENT>0001284084-18-000029.txt : 20180329
<SEC-HEADER>0001284084-18-000029.hdr.sgml : 20180329
<ACCEPTANCE-DATETIME>20180329151328
ACCESSION NUMBER:		0001284084-18-000029
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20171205
FILED AS OF DATE:		20180329
DATE AS OF CHANGE:		20180329

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			The Ronald D Croatti Trust - 1993
		CENTRAL INDEX KEY:			0001724901

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-08504
		FILM NUMBER:		18722613

	MAIL ADDRESS:	
		STREET 1:		C/O CAROL CROATTI
		STREET 2:		21 JEFFERSON DRIVE
		CITY:			LONDONDERRY
		STATE:			NH
		ZIP:			03053

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			UNIFIRST CORP
		CENTRAL INDEX KEY:			0000717954
		STANDARD INDUSTRIAL CLASSIFICATION:	SERVICES-PERSONAL SERVICES [7200]
		IRS NUMBER:				042103460
		STATE OF INCORPORATION:			MA
		FISCAL YEAR END:			0830

	BUSINESS ADDRESS:	
		STREET 1:		68 JONSPIN RD
		CITY:			WILMINGTON
		STATE:			MA
		ZIP:			01887
		BUSINESS PHONE:		(978) 658-8888

	MAIL ADDRESS:	
		STREET 1:		68 JONSPIN ROAD
		CITY:			WILMINGTON
		STATE:			MA
		ZIP:			01887

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	INTERSTATE UNIFORM SERVICES CORP/MA
		DATE OF NAME CHANGE:	19840410
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>wf-form4_152235077399375.xml
<DESCRIPTION>FORM 4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2017-12-05</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000717954</issuerCik>
        <issuerName>UNIFIRST CORP</issuerName>
        <issuerTradingSymbol>UNF</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001724901</rptOwnerCik>
            <rptOwnerName>The Ronald D Croatti Trust - 1993</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>68 JONSPIN ROAD</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>WILMINGTON</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>01887</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2017-12-05</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>5</transactionFormType>
                <transactionCode>W</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value>E</value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>31134</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>31134</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Class B Common Stock</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F1"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2017-12-05</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>5</transactionFormType>
                <transactionCode>W</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value>E</value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>1098770</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F1"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock ($0.10 par value)</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>1098770.0</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1098770</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
        <derivativeHolding>
            <securityTitle>
                <value>Class B Common Stock</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F1"/>
            </conversionOrExercisePrice>
            <exerciseDate>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F1"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock ($0.10 par value)</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>2750905.0</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>2750905</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                    <footnoteId id="F4"/>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Partnership</value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeHolding>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Each share of Class B Common Stock is convertible at any time by the holder into one share of Common Stock.  Each share of Class B Common Stock automatically converts into one share of Common Stock upon transfer to a recipient that is not a permitted transferee or upon termination of the Class B Common Stock, in each case in accordance with the terms of the charter of UniFirst Corporation.</footnote>
        <footnote id="F2">Includes 1,734,986 shares owned directly by The Queue Limited Partnership and 199 shares owned directly by Queue Management Associates, Inc.  Queue Management Associates, Inc. is the general partner of The Queue Limited Partnership. The Ronald D. Croatti Trust  1993 (of which Carol Croatti and Matthew Croatti are the trustees and Carol Croatti is the beneficiary), Cynthia Croatti and Cecilia Levenstein are the sole shareholders of Queue Management Associates, Inc., and Carol Croatti, Cynthia Croatti and Cecelia Levenstein are the directors of Queue Management Associates, Inc. Cynthia Croatti and Cecelia Levenstein are trustees, co-trustees and in some cases beneficiaries, and in some cases their children are beneficiaries, of various trusts which hold limited partnership interests in The Queue Limited Partnership.  Ronald D. Croatti's children are beneficiaries of certain trusts which hold limited partnership interests in The Queue Limited Partnership.</footnote>
        <footnote id="F3">Includes 1,015,717 shares owned directly by The Red Cat Limited Partnership and 3 shares owned directly by Red Cat Management Associates, Inc.  Red Cat Management Associates, Inc. is the general partner of The Red Cat Limited Partnership. The Ronald D. Croatti Trust - 1993 and Cynthia Croatti are the sole shareholders of Red Cat Management Associates, Inc. and Carol Croatti and Cynthia Croatti are the directors of Red Cat Management Associates, Inc. Cynthia Croatti and Cecelia Levenstein are trustees, co-trustees and in the case of Cynthia Croatti a beneficiary of certain trusts which hold limited partnership interests in The Red Cat Limited Partnership. Ronald D. Croatti's children are beneficiaries of a trust which hold limited partnership interests in The Red Cat Limited Partnership.</footnote>
        <footnote id="F4">Each of the aforementioned reporting persons disclaims beneficial ownership of these reported securities, except to the extent of his, her or its pecuniary interest, if any, therein, and this report shall not be deemed an admission that such persons are the beneficial owners of these securities for purposes of Section 16 or any other purpose.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ David Whitman, Attorney-in-Fact</signatureName>
        <signatureDate>2018-03-29</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
