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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2020-10-23</periodOfReport>

    <notSubjectToSection16>1</notSubjectToSection16>

    <issuer>
        <issuerCik>0000722830</issuerCik>
        <issuerName>IMMUNOMEDICS INC</issuerName>
        <issuerTradingSymbol>IMMU</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001754157</rptOwnerCik>
            <rptOwnerName>Freedberg Jared</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O IMMUNOMEDICS, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>300 THE AMERICAN ROAD</rptOwnerStreet2>
            <rptOwnerCity>MORRIS PLAINS</rptOwnerCity>
            <rptOwnerState>NJ</rptOwnerState>
            <rptOwnerZipCode>07950</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Gen. Counsel &amp; Corp. Secretary</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Stock Option (Right to Buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F1"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2020-10-23</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>D</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>280105</value>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F1"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>280105</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">In connection with the consummation of the Merger, at the Effective Time, each option to purchase shares of Common Stock (&quot;Stock Option&quot;) that was outstanding as of immediately prior to the Effective Time, whether vested or not vested, was automatically cancelled and converted into the right to receive an amount in cash equal to (i) the excess, if any, of the Offer Price over the exercise price payable per share subject to such Stock Option, multiplied by (ii) the total number of shares of Common Stock subject to such Stock Option immediately prior to the Effective Time. Any Stock Option that had an exercise price per share that was equal to or greater than the Offer Price was cancelled for no consideration.</footnote>
    </footnotes>

    <remarks>This Form 4 reports securities disposed of under the terms of the Agreement and Plan of Merger (the ''Agreement''), dated as of September 13, 2020, by and among Immunomedics, Inc. (the ''Company''), Gilead Sciences, Inc. (''Parent''), and Maui Merger Sub Inc., a wholly owned subsidiary of Parent (''Merger Sub'').  Pursuant to the Agreement, on October 23, 2020 (the ''Effective Time''), Merger Sub merged with and into the Company, with the Company becoming a wholly owned subsidiary of Parent (the ''Merger''). In connection with the consummation of the Merger, at the Effective Time, each share of common stock, par value $0.01 per share, of the Company (''Common Stock'') that was outstanding immediately prior to the Effective Time (other than certain shares specified in the Agreement) was automatically cancelled and converted into the right to receive $88.00 in cash (the ''Offer Price''), without interest and subject to required withholding taxes.A copy of the Agreement is included as Exhibit 2.1 to the Company's Form 8-K filed with the SEC on September 14, 2020.</remarks>

    <ownerSignature>
        <signatureName>/s/ Jared Freedberg</signatureName>
        <signatureDate>2020-10-23</signatureDate>
    </ownerSignature>
</ownershipDocument>
