<?xml version="1.0" encoding="utf-8"?>
<ownershipDocument>
    <schemaVersion>X0201</schemaVersion>

    <documentType>4</documentType>
  <periodOfReport>2004-01-15</periodOfReport>
  <notSubjectToSection16>0</notSubjectToSection16>
    <issuer>
        <issuerCik>0000034408</issuerCik>
        <issuerName>FAMILY DOLLAR STORES INC</issuerName>
        <issuerTradingSymbol>FDO</issuerTradingSymbol>
  </issuer>
  <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001222830</rptOwnerCik>
            <rptOwnerName>BERNSTEIN MARK R</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>THREE WACHOVIA CENTER</rptOwnerStreet1>
            <rptOwnerStreet2>401 S. TRYON STREET, SUITE 3000</rptOwnerStreet2>
            <rptOwnerCity>CHARLOTTE</rptOwnerCity>
            <rptOwnerState>NC</rptOwnerState>
            <rptOwnerZipCode>28202</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
            <reportingOwnerRelationship>
      <isDirector>1</isDirector>
      <isOfficer>0</isOfficer>
      <isTenPercentOwner>0</isTenPercentOwner>
      <isOther>0</isOther>
    </reportingOwnerRelationship>
  </reportingOwner>
  <nonDerivativeTable>
    <nonDerivativeTransaction>
      <securityTitle>
        <value>Common Stock</value>
      </securityTitle>
      <transactionDate>
        <value>2003-10-21</value>
      </transactionDate>
      <transactionCoding>
        <transactionFormType>5</transactionFormType>
        <transactionCode>G</transactionCode>
        <equitySwapInvolved>0</equitySwapInvolved>
      </transactionCoding>
      <transactionTimeliness>
        <value>E</value>
      </transactionTimeliness>
      <transactionAmounts>
        <transactionShares>
          <value>500</value>
        </transactionShares>
        <transactionPricePerShare>
          <value>0</value>
          <footnoteId id="F2"/>
        </transactionPricePerShare>
        <transactionAcquiredDisposedCode>
          <value>D</value>
        </transactionAcquiredDisposedCode>
      </transactionAmounts>
      <postTransactionAmounts>
        <sharesOwnedFollowingTransaction>
          <value>18250</value>
        </sharesOwnedFollowingTransaction>
      </postTransactionAmounts>
      <ownershipNature>
        <directOrIndirectOwnership>
          <value>I</value>
        </directOrIndirectOwnership>
        <natureOfOwnership>
          <value>By Wife</value>
        </natureOfOwnership>
      </ownershipNature>
    </nonDerivativeTransaction>
    <nonDerivativeTransaction>
      <securityTitle>
        <value>Common Stock</value>
      </securityTitle>
      <transactionDate>
        <value>2003-10-21</value>
      </transactionDate>
      <transactionCoding>
        <transactionFormType>5</transactionFormType>
        <transactionCode>G</transactionCode>
        <equitySwapInvolved>0</equitySwapInvolved>
      </transactionCoding>
      <transactionTimeliness>
        <value>E</value>
      </transactionTimeliness>
      <transactionAmounts>
        <transactionShares>
          <value>742</value>
        </transactionShares>
        <transactionPricePerShare>
          <value>0</value>
          <footnoteId id="F2"/>
        </transactionPricePerShare>
        <transactionAcquiredDisposedCode>
          <value>D</value>
        </transactionAcquiredDisposedCode>
      </transactionAmounts>
      <postTransactionAmounts>
        <sharesOwnedFollowingTransaction>
          <value>4838</value>
        </sharesOwnedFollowingTransaction>
      </postTransactionAmounts>
      <ownershipNature>
        <directOrIndirectOwnership>
          <value>D</value>
        </directOrIndirectOwnership>
      </ownershipNature>
    </nonDerivativeTransaction>
    <nonDerivativeTransaction>
      <securityTitle>
        <value>Common Stock</value>
      </securityTitle>
      <transactionDate>
        <value>2004-01-15</value>
        <footnoteId id="F1"/>
      </transactionDate>
      <transactionCoding>
        <transactionFormType>4</transactionFormType>
        <transactionCode>A</transactionCode>
        <equitySwapInvolved>0</equitySwapInvolved>
      </transactionCoding>
      <transactionTimeliness>
        <value></value>
      </transactionTimeliness>
      <transactionAmounts>
        <transactionShares>
          <value>594</value>
        </transactionShares>
        <transactionPricePerShare>
          <value>0</value>
          <footnoteId id="F1"/>
        </transactionPricePerShare>
        <transactionAcquiredDisposedCode>
          <value>A</value>
        </transactionAcquiredDisposedCode>
      </transactionAmounts>
      <postTransactionAmounts>
        <sharesOwnedFollowingTransaction>
          <value>5432</value>
        </sharesOwnedFollowingTransaction>
      </postTransactionAmounts>
      <ownershipNature>
        <directOrIndirectOwnership>
          <value>D</value>
        </directOrIndirectOwnership>
      </ownershipNature>
    </nonDerivativeTransaction>
  </nonDerivativeTable>
  <footnotes>
    <footnote id="F1">Grant of Common Stock made pursuant to shareholder approved Family Dollar 2000 Outside Directors Plan. </footnote>
    <footnote id="F2">Gift</footnote>
  </footnotes>
  <ownerSignature>
    <signatureName>/s/ Mark R. Bernstein</signatureName>
    <signatureDate>2004-01-19</signatureDate>
  </ownerSignature>
</ownershipDocument>

