<SUBMISSION>
<ACCESSION-NUMBER>0000706688-19-000041
<TYPE>4
<PUBLIC-DOCUMENT-COUNT>1
<PERIOD>20190221
<FILING-DATE>20190225
<DATE-OF-FILING-DATE-CHANGE>20190225
<REPORTING-OWNER>
<OWNER-DATA>
<CONFORMED-NAME>Doman Curtis Linn
<CIK>0001650671
</OWNER-DATA>
<FILING-VALUES>
<FORM-TYPE>4
<ACT>34
<FILE-NUMBER>001-13941
<FILM-NUMBER>19631475
</FILING-VALUES>
<MAIL-ADDRESS>
<STREET1>309 E. PACES FERRY ROAD
<CITY>ATLANTA
<STATE>GA
<ZIP>30305
</MAIL-ADDRESS>
</REPORTING-OWNER>
<ISSUER>
<COMPANY-DATA>
<CONFORMED-NAME>AARON'S INC
<CIK>0000706688
<ASSIGNED-SIC>7359
<IRS-NUMBER>580687630
<STATE-OF-INCORPORATION>GA
<FISCAL-YEAR-END>1231
</COMPANY-DATA>
<BUSINESS-ADDRESS>
<STREET1>400 GALLERIA PARKWAY SE
<STREET2>SUITE 300
<CITY>ATLANTA
<STATE>GA
<ZIP>30339
<PHONE>678-402-3000
</BUSINESS-ADDRESS>
<MAIL-ADDRESS>
<STREET1>400 GALLERIA PARKWAY SE
<STREET2>SUITE 300
<CITY>ATLANTA
<STATE>GA
<ZIP>30339
</MAIL-ADDRESS>
<FORMER-COMPANY>
<FORMER-CONFORMED-NAME>AARON RENTS INC
<DATE-CHANGED>19920703
</FORMER-COMPANY>
</ISSUER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>wf-form4_155114930021035.xml
<DESCRIPTION>FORM 4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2019-02-21</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000706688</issuerCik>
        <issuerName>AARON'S INC</issuerName>
        <issuerTradingSymbol>AAN</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001650671</rptOwnerCik>
            <rptOwnerName>Doman Curtis Linn</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>400 GALLERIA PARKWAY SE, SUITE 300</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>ATLANTA</rptOwnerCity>
            <rptOwnerState>GA</rptOwnerState>
            <rptOwnerZipCode>30339</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>CPO Progressive Leasing</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2019-02-21</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>15075</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>54.18</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>132598</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2019-02-21</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>6600</value>
                    <footnoteId id="F3"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>54.18</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>139198</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>72000</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>LLC</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Stock Options (Right to Buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>54.18</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2019-02-21</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>18360</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2020-03-07</value>
                <footnoteId id="F4"/>
            </exerciseDate>
            <expirationDate>
                <value>2029-02-21</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>18360.0</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>18360</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">On February 21, 2019, the Compensation Committee of the Issuer's Board of Directors determined these performance shares were earned, based on the level of attainment of various financial performance goals.  These shares, which were granted in March 2018, are expected to vest in three equal increments on each of March 7, 2019, 2020 and 2021, subject to the grant agreement between the Issuer and the Reporting Person.</footnote>
        <footnote id="F2">The reporting person reported sales of an aggregate of 55,000 shares during the period from May 2, 2018 through November 6, 2018 pursuant to Rule 10b5-1 trading plans adopted by the reporting person. These shares were incorrectly reported as being sold from the reporting person's direct holdings rather than the reporting person's indirect holdings. As a result, this Form 4 updates the reporting person's direct and indirect holdings to accurately reflect the sale of shares from the reporting person's indirect holdings.</footnote>
        <footnote id="F3">Restricted stock award which is expected to vest in three equal increments on each of March 7, 2020, 2021 and 2022, subject to the grant agreement between the Issuer and the Reporting Person.</footnote>
        <footnote id="F4">Stock option award is expected to vest in three equal increments on each of March 7, 2020, 2021 and 2022, subject to the grant agreement between the Issuer and the Reporting Person.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Robert P. Sinclair, by Power of Attorney for Curtis L. Doman</signatureName>
        <signatureDate>2019-02-25</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SUBMISSION>
