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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2018-05-29</periodOfReport>

    <issuer>
        <issuerCik>0000091419</issuerCik>
        <issuerName>J M SMUCKER Co</issuerName>
        <issuerTradingSymbol>SJM</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001251529</rptOwnerCik>
            <rptOwnerName>BELGYA MARK R</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>ONE STRAWBERRY LANE</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>ORRVILLE</rptOwnerCity>
            <rptOwnerState>OH</rptOwnerState>
            <rptOwnerZipCode>44667-0280</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isOfficer>1</isOfficer>
            <officerTitle>Vice Chair and CFO</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Option Common Shares</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>111.86</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2018-05-29</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>12500</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2018-05-29</value>
            </exerciseDate>
            <expirationDate>
                <value>2025-03-19</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Shares</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>12500</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>12500</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
        <derivativeHolding>
            <securityTitle>
                <value>Option Common Shares</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>111.86</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2017-06-15</value>
            </exerciseDate>
            <expirationDate>
                <value>2025-03-19</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Shares</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>25000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>25000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">On March 19, 2015, the reporting person was granted a performance-based non-statutory stock option to purchase 75,000 shares of common stock.  The option vests in 3 equal annual installments based 50% on the Company's achievement of &quot;synergy realization&quot; performance objectives and 50% on the Company's achievement of EBITDA performance objectives for each of the fiscal years ending April 30, 2016, 2017, and 2018.  The &quot;synergy realization&quot; objective for the fiscal year ending April 30, 2018 was met, resulting in vesting of one-sixth of the total shares subject to the option.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Jeannette L. Knudsen, POA</signatureName>
        <signatureDate>2018-05-31</signatureDate>
    </ownerSignature>
</ownershipDocument>
