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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4/A</documentType>

    <periodOfReport>2020-11-12</periodOfReport>

    <dateOfOriginalSubmission>2020-11-16</dateOfOriginalSubmission>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001333822</issuerCik>
        <issuerName>SemiLEDs Corp</issuerName>
        <issuerTradingSymbol>LEDS</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001713973</rptOwnerCik>
            <rptOwnerName>Lee Roger</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O SEMILEDS CORPORATION</rptOwnerStreet1>
            <rptOwnerStreet2>3F, NO. 11 KE JUNG RD., CHU-NAN SITE</rptOwnerStreet2>
            <rptOwnerCity>TAIWAN</rptOwnerCity>
            <rptOwnerState>F5</rptOwnerState>
            <rptOwnerZipCode>00000</rptOwnerZipCode>
            <rptOwnerStateDescription>TAIWAN, PROVINCE OF CHINA</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>2020-11-12</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>5000</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>7500</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">These shares represented stock units and will be settled in LEDS stock upon vesting, 25% of the restricted stock units will vest on Feb 12, 2021, May 12, 2021, Aug 12, 2021 and Nov 12, 2021, so long as the Reporting Person's continuous service through the applicable vesting date. In the event that the 2021 annual meeting falls before Nov 12, 2021, 100% of the stock units shall immediately vest on the date of the 2021 annual meeting. Vested shares will be delivered to the person within the first open trading window following the vesting date, but in no event later than the 15th day of the 3rd following the end of the Company's tax year that includes the vesting date.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Roger Lee</signatureName>
        <signatureDate>2020-11-30</signatureDate>
    </ownerSignature>
</ownershipDocument>
