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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2019-06-03</periodOfReport>

    <issuer>
        <issuerCik>0001324948</issuerCik>
        <issuerName>RBC Bearings INC</issuerName>
        <issuerTradingSymbol>ROLL</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001204696</rptOwnerCik>
            <rptOwnerName>BERGERON DANIEL A</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>129 PEACEABLE STREET</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>REDDING</rptOwnerCity>
            <rptOwnerState>CT</rptOwnerState>
            <rptOwnerZipCode>06896</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>true</isDirector>
            <isOfficer>true</isOfficer>
            <isTenPercentOwner>false</isTenPercentOwner>
            <isOther>false</isOther>
            <officerTitle>VP, CFO and COO</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2019-06-03</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>false</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>25000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>89244</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                    <footnoteId id="F4"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Option to Purchase Common Stock</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>143.92</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2019-06-03</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>false</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>35000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2020-06-03</value>
                <footnoteId id="F5"/>
            </exerciseDate>
            <expirationDate>
                <value>2026-06-03</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>35000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>35000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
        <derivativeHolding>
            <securityTitle>
                <value>Option to Purchase Common Stock</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>51.08</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2014-06-14</value>
            </exerciseDate>
            <expirationDate>
                <value>2020-06-14</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>20000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>20000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Option to Purchase Common Stock</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>64.15</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2015-07-01</value>
                <footnoteId id="F6"/>
            </exerciseDate>
            <expirationDate>
                <value>2021-07-01</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>20000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>20000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Option to Purchase Common Stock</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>72.83</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2016-07-01</value>
                <footnoteId id="F7"/>
            </exerciseDate>
            <expirationDate>
                <value>2022-07-01</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>25000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>25000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Option to Purchase Common Stock</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>72.94</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2017-07-08</value>
                <footnoteId id="F8"/>
            </exerciseDate>
            <expirationDate>
                <value>2023-07-08</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>40000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>40000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Option to Purchase Common Stock</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>99.64</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2018-06-27</value>
                <footnoteId id="F9"/>
            </exerciseDate>
            <expirationDate>
                <value>2024-06-27</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>30000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>30000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Option to Purchase Common Stock</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>132.12</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2019-06-07</value>
                <footnoteId id="F10"/>
            </exerciseDate>
            <expirationDate>
                <value>2025-06-07</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>35000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>35000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">25,000 shares of the reported Common Stock are Restricted Shares. 1/3 vest on 6/3/2020, 1/3 vest on 6/3/2021 and 1/3 vest on 6/3/2022. Unvested shares of Restricted Stock (i) may be immediately forfeited to the Company at the time the grantee ceases to be an officer or employee of, or otherwise perform services for, the Company or its subsidiaries under certain circumstances or (ii) may lapse upon the happening of certain events.</footnote>
        <footnote id="F2">25,000 shares of the reported Common Stock are Restricted Shares. 1/3 vest on 6/7/2019, 1/3 vest on 6/7/2020 and 1/3 vest on 6/7/2021. Unvested shares of Restricted Stock (i) may be immediately forfeited to the Company at the time the grantee ceases to be an officer or employee of, or otherwise perform services for, the company or its subsidiaries under certain circumstances or (ii) may lapse upon the happening of certain events.</footnote>
        <footnote id="F3">3,333 shares of the reported Common Stock are Restricted Shares. The Restrictions lapse on 7/8/2019. Unvested shares of Restricted Stock (i) may be immediately forfeited to the Company at the time the grantee ceases to be an officer or employee of, or otherwise perform services for, the Company or its subsidiaries under certain circumstances or (ii) may lapse upon the happening of certain events.</footnote>
        <footnote id="F4">6,667 shares of the reported Common Stock are Restricted Shares. The Restrictions lapse in accordance with the following schedule - 1/2 vest on 6/27/2019 and 1/2 vest on 6/27/2020. Unvested shares of Restricted Stock (i) may be immediately forfeited to the Company at the time the grantee ceases to be an officer or employee of, or otherwise perform services for, the Company or its subsidiaries under certain circumstances or (ii) may lapse upon the happening of certain events.</footnote>
        <footnote id="F5">Options to purchase shares of Common Stock are subject to the following vesting schedule - 1/5 vest on 6/3/2020, 1/5 vest on 6/3/2021, 1/5 vest on 6/3/2022, 1/5 vest on 6/3/2023 and 1/5 vest on 6/3/2024.</footnote>
        <footnote id="F6">All these options to purchase Common Stock are exercisable except for 4,000 options that vest on 7/1/2019.</footnote>
        <footnote id="F7">All these options to purchase Common Stock are exercisable except for 8,000 options that are subject to the following vesting schedule - 1/2 vest on 7/1/2019 and 1/2 vest on 7/1/2020.</footnote>
        <footnote id="F8">All these options to purchase Common Stock are exercisable except for 24,000 options that are subject to the following vesting schedule - 1/3 vest on 7/8/2019, 1/3 vest on 7/8/2020 and 1/3 vest on 7/8/2021.</footnote>
        <footnote id="F9">All these options to purchase Common Stock are exercisable except for 24,000 options that are subject to the following vesting schedule - 1/4 vest on 6/27/2019, 1/4 vest on 6/27/2020, 1/4 vest on 6/27/2021 and 1/4 vest on 6/27/2022.</footnote>
        <footnote id="F10">Options to purchase shares of Common Stock are subject to the following vesting schedule - 1/5 vest on 6/7/2019, 1/5 vest on 6/7/2020, 1/5 vest on 6/7/2021, 1/5 vest on 6/7/2022 and 1/5 vest on 6/7/2023.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/Joseph Salamunovich/attorney in fact</signatureName>
        <signatureDate>2019-06-05</signatureDate>
    </ownerSignature>
</ownershipDocument>
