<SEC-DOCUMENT>0001666138-18-000106.txt : 20180904
<SEC-HEADER>0001666138-18-000106.hdr.sgml : 20180904
<ACCEPTANCE-DATETIME>20180904181651
ACCESSION NUMBER:		0001666138-18-000106
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20180904
FILED AS OF DATE:		20180904
DATE AS OF CHANGE:		20180904

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Johnson David Paul
		CENTRAL INDEX KEY:			0001748246

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-37793
		FILM NUMBER:		181053405

	MAIL ADDRESS:	
		STREET 1:		16100 SOUTH LATHROP AVENUE
		CITY:			HARVEY
		STATE:			IL
		ZIP:			60426

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			Atkore International Group Inc.
		CENTRAL INDEX KEY:			0001666138
		STANDARD INDUSTRIAL CLASSIFICATION:	MISCELLANEOUS ELECTRICAL MACHINERY, EQUIPMENT & SUPPLIES [3690]
		IRS NUMBER:				900631463
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			0930

	BUSINESS ADDRESS:	
		STREET 1:		16100 SOUTH LATHROP AVENUE
		CITY:			HARVEY
		STATE:			IL
		ZIP:			60426
		BUSINESS PHONE:		7083391610

	MAIL ADDRESS:	
		STREET 1:		16100 SOUTH LATHROP AVENUE
		CITY:			HARVEY
		STATE:			IL
		ZIP:			60426
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>wf-form4_153609939566853.xml
<DESCRIPTION>FORM 4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2018-09-04</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001666138</issuerCik>
        <issuerName>Atkore International Group Inc.</issuerName>
        <issuerTradingSymbol>ATKR</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001748246</rptOwnerCik>
            <rptOwnerName>Johnson David Paul</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>16100 S. LATHROP AVENUE</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>HARVEY</rptOwnerCity>
            <rptOwnerState>IL</rptOwnerState>
            <rptOwnerZipCode>60426</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Vice President and CFO</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
                <footnoteId id="F1"/>
            </securityTitle>
            <transactionDate>
                <value>2018-09-04</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>25567</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>25567</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">Represents restricted stock units (&quot;RSUs&quot;). The RSUs vest, subject to continued employment, in three installments as follows: 60% on the first anniversary of the grant date; 20% on the second anniversary of the grant date; and 20% on the third anniversary of the grant date. The RSUs settle into common stock of the issuer no later than March 15th of the calendar year immediately following the calendar year in which vesting occurs.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Daniel S. Kelly, Attorney-in-Fact for David P. Johnson</signatureName>
        <signatureDate>2018-09-04</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
