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

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2005-04-21</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000088948</issuerCik>
        <issuerName>SENECA FOODS CORP /NY/</issuerName>
        <issuerTradingSymbol>SENEA</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0000101063</rptOwnerCik>
            <rptOwnerName>CHIQUITA BRANDS INTERNATIONAL INC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1></rptOwnerStreet1>
            <rptOwnerStreet2>250 EAST FIFTH STREET</rptOwnerStreet2>
            <rptOwnerCity>CINCINNATI</rptOwnerCity>
            <rptOwnerState>OH</rptOwnerState>
            <rptOwnerZipCode>45202</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>1</isOther>
            <otherText>Former 10% Owner</otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Convertible Preferred Stock Series 2003</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F1"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2005-04-21</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>967742</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>15</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2003-05-27</value>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F1"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock Class A par value $.25 per share</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>967742</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By a subsidiary</value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">The Convertible Preferred Stock Series 2003 is convertible into common stock on a one-for-one basis and has no expiration date.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>John W. Braukman, III, Senior Vice President and Chief Financial Officer</signatureName>
        <signatureDate>2005-04-22</signatureDate>
    </ownerSignature>
</ownershipDocument>
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X0202
4
2005-04-21
0
0000088948
SENECA FOODS CORP /NY/
SENEA
0000101063
CHIQUITA BRANDS INTERNATIONAL INC
250 EAST FIFTH STREET
CINCINNATI
OH
45202
0
0
0
1
Former 10% Owner
Convertible Preferred Stock Series 2003
2005-04-21
4
S
0
967742
15
D
2003-05-27
Common Stock Class A par value $.25 per share
967742
0
I
By a subsidiary
The Convertible Preferred Stock Series 2003 is convertible into common stock on a one-for-one basis and has no expiration date.
John W. Braukman, III, Senior Vice President and Chief Financial Officer
2005-04-22