<SEC-DOCUMENT>0000089439-18-000061.txt : 20180727
<SEC-HEADER>0000089439-18-000061.hdr.sgml : 20180727
<ACCEPTANCE-DATETIME>20180727113410
ACCESSION NUMBER:		0000089439-18-000061
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20180726
FILED AS OF DATE:		20180727
DATE AS OF CHANGE:		20180727

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Millerchip Mark
		CENTRAL INDEX KEY:			0001550386

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-06770
		FILM NUMBER:		18973887

	MAIL ADDRESS:	
		STREET 1:		8285 TOURNAMENT DRIVE SUITE 150
		CITY:			MEMPHIS
		STATE:			TN
		ZIP:			38125

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			MUELLER INDUSTRIES INC
		CENTRAL INDEX KEY:			0000089439
		STANDARD INDUSTRIAL CLASSIFICATION:	ROLLING DRAWING & EXTRUDING OF NONFERROUS METALS [3350]
		IRS NUMBER:				250790410
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		SUITE 150
		STREET 2:		8285 TOURNAMENT DRIVE
		CITY:			MEMPHIS
		STATE:			TN
		ZIP:			38125
		BUSINESS PHONE:		(901)753-3200

	MAIL ADDRESS:	
		STREET 1:		SUITE 150
		STREET 2:		8285 TOURNAMENT DRIVE
		CITY:			MEMPHIS
		STATE:			TN
		ZIP:			38125

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	SHARON STEEL CORP
		DATE OF NAME CHANGE:	19910103
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>wf-form4_153270563575737.xml
<DESCRIPTION>FORM 4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2018-07-26</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000089439</issuerCik>
        <issuerName>MUELLER INDUSTRIES INC</issuerName>
        <issuerTradingSymbol>MLI</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001550386</rptOwnerCik>
            <rptOwnerName>Millerchip Mark</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>8285 TOURNAMENT DRIVE SUITE 150</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>MEMPHIS</rptOwnerCity>
            <rptOwnerState>TN</rptOwnerState>
            <rptOwnerZipCode>38125</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Exec. Director - European Ops</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable></nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Phantom Stock</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>0.0</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2018-07-26</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>13000</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2023-07-31</value>
            </exerciseDate>
            <expirationDate>
                <value>2023-07-31</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>13000.0</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>13000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Each share of phantom stock is the equivalent of one share of MLI common stock. The shares of phantom stock will be settled in cash based on the value of MLI's common stock on the vest date.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>Anthony Steinriede, Attorney-in-Fact</signatureName>
        <signatureDate>2018-07-27</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
