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

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2007-10-24</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000100726</issuerCik>
        <issuerName>UNIFI INC</issuerName>
        <issuerTradingSymbol>UFI</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001360013</rptOwnerCik>
            <rptOwnerName>BERRIER R ROGER JR</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>148 BROADMOOR DRIVE</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>ADVANCE</rptOwnerCity>
            <rptOwnerState>NC</rptOwnerState>
            <rptOwnerZipCode>27006</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Executive Vice President</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Stock Options (Right to Buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>2.72</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2007-10-24</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>300000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <value>2017-10-24</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>300000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>300000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">The Options granted shall vest and become exercisable on the date that the closing price of the Registrant's common stock on the New York Stock Exchange shall have been at least $6.00 per share for thirty (30) consecutive trading days.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/R. Roger Berrier, Jr.</signatureName>
        <signatureDate>2007-10-25</signatureDate>
    </ownerSignature>
</ownershipDocument>
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X0202
4
2007-10-24
0
0000100726
UNIFI INC
UFI
0001360013
BERRIER R ROGER JR
148 BROADMOOR DRIVE
ADVANCE
NC
27006
1
1
0
0
Executive Vice President
Stock Options (Right to Buy)
2.72
2007-10-24
4
A
0
300000
0
A
2017-10-24
Common Stock
300000
300000
D
The Options granted shall vest and become exercisable on the date that the closing price of the Registrant's common stock on the New York Stock Exchange shall have been at least $6.00 per share for thirty (30) consecutive trading days.
/s/R. Roger Berrier, Jr.
2007-10-25