<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0303</schemaVersion>

    <documentType>5</documentType>

    <periodOfReport>2010-12-31</periodOfReport>

    <form3HoldingsReported>0</form3HoldingsReported>

    <form4TransactionsReported>0</form4TransactionsReported>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001201396</rptOwnerCik>
            <rptOwnerName>BENATAR  LEO</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>309 E. PACES FERRY ROAD, N.E.</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>ATLANTA</rptOwnerCity>
            <rptOwnerState>GA</rptOwnerState>
            <rptOwnerZipCode>30305-</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2010-12-14</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>5</transactionFormType>
                <transactionCode>G</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>3000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>20.28</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>12832</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F2"/>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">1,000 shares pertain to restricted common stock granted on November 7, 2006</footnote>
        <footnote id="F2">Reflects (i) the automatic conversion on December 10, 2010 of each outstanding share of the Company's nonvoting Common Stock, Par Value $0.50 Per Share, into one share of the Company's Class A Common Stock, Par Value $0.50 Per Share and (ii) the simultaneous redesignation of the Class A Common Stock, Par Value $0.50 Per Share, as Common Stock, Par Value $0.50 Per Share, pursuant to the Amended and Restated Certificate of Incorporation of the Company effective December 10, 2010.  Immediately prior to the automatic conversion, the reporting person held 11,160 shares of Common Stock and 4,672 shares of Class A Common Stock.  Such share conversion was an exempt transaction pursuant to SEC Rule 16b-7.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Robert Sinclair, by Power of Attorney for Leo Benatar</signatureName>
        <signatureDate>2011-02-14</signatureDate>
    </ownerSignature>
</ownershipDocument>
