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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2020-05-22</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001610250</issuerCik>
        <issuerName>Boot Barn Holdings, Inc.</issuerName>
        <issuerTradingSymbol>BOOT</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001623534</rptOwnerCik>
            <rptOwnerName>Conroy James Grant</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O BOOT BARN HOLDINGS, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>15345 BARRANCA PKWY</rptOwnerStreet2>
            <rptOwnerCity>IRVINE</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>92618</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Chief Executive Officer</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2020-05-22</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>27509</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
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                <sharesOwnedFollowingTransaction>
                    <value>57328</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2020-05-24</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>F</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F3"/>
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            <transactionAmounts>
                <transactionShares>
                    <value>795</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>21.86</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
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                <sharesOwnedFollowingTransaction>
                    <value>16813</value>
                    <footnoteId id="F4"/>
                </sharesOwnedFollowingTransaction>
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            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
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        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
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                <sharesOwnedFollowingTransaction>
                    <value>55029</value>
                    <footnoteId id="F5"/>
                </sharesOwnedFollowingTransaction>
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                    <value>D</value>
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            <conversionOrExercisePrice>
                <value>20.94</value>
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                <value>2020-05-22</value>
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                    <value>38957</value>
                </transactionShares>
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                <transactionAcquiredDisposedCode>
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            <exerciseDate>
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            <expirationDate>
                <value>2030-05-21</value>
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            <underlyingSecurity>
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                </underlyingSecurityTitle>
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                </sharesOwnedFollowingTransaction>
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            <securityTitle>
                <value>Options</value>
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            <conversionOrExercisePrice>
                <value>24.08</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2020-05-22</value>
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                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
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            <transactionAmounts>
                <transactionShares>
                    <value>41579</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
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                <transactionAcquiredDisposedCode>
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            <expirationDate>
                <value>2030-05-21</value>
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            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
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                <underlyingSecurityShares>
                    <value>41579</value>
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                    <value>41579</value>
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            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
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        <derivativeHolding>
            <securityTitle>
                <value>Options</value>
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                <value>28.82</value>
            </conversionOrExercisePrice>
            <exerciseDate>
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            <expirationDate>
                <value>2023-06-09</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>58553</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
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                </sharesOwnedFollowingTransaction>
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            <ownershipNature>
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                    <value>D</value>
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        <derivativeHolding>
            <securityTitle>
                <value>Options</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>7.11</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <footnoteId id="F7"/>
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            <expirationDate>
                <value>2024-05-20</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>57136</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>57136</value>
                </sharesOwnedFollowingTransaction>
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            <ownershipNature>
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                    <value>D</value>
                </directOrIndirectOwnership>
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        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Options</value>
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            <conversionOrExercisePrice>
                <value>6.15</value>
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            <exerciseDate>
                <footnoteId id="F7"/>
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            <expirationDate>
                <value>2025-06-05</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>75904</value>
                </underlyingSecurityShares>
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                    <value>75904</value>
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                    <value>D</value>
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        <derivativeHolding>
            <securityTitle>
                <value>Options</value>
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                <value>23.92</value>
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            <expirationDate>
                <value>2026-05-24</value>
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            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
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                <underlyingSecurityShares>
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                    <value>D</value>
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            <securityTitle>
                <value>Options</value>
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            <conversionOrExercisePrice>
                <value>28.63</value>
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            <exerciseDate>
                <footnoteId id="F8"/>
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            <expirationDate>
                <value>2029-05-20</value>
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            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>227273</value>
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                <sharesOwnedFollowingTransaction>
                    <value>227273</value>
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            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
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        <derivativeHolding>
            <securityTitle>
                <value>Options</value>
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            <conversionOrExercisePrice>
                <value>28.63</value>
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            <exerciseDate>
                <footnoteId id="F6"/>
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            <expirationDate>
                <value>2029-05-20</value>
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            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>37760</value>
                </underlyingSecurityShares>
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                <sharesOwnedFollowingTransaction>
                    <value>37760</value>
                </sharesOwnedFollowingTransaction>
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                    <value>D</value>
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        </derivativeHolding>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Consists of shares underlying restricted stock units granted under the Company's 2014 Equity Incentive Plan, subject to vesting over a four-year period in equal annual installments on each anniversary of the grant date.</footnote>
        <footnote id="F2">Consists of the total number of shares of common stock underlying restricted stock units held by the reporting person as of May 22, 2020 that remain subject to time-based vesting.</footnote>
        <footnote id="F3">On May 24, 2020, in connection with the vesting of shares underlying 2,299 previously disclosed restricted stock units, the issuer withheld 795 shares of common stock to satisfy withholding taxes due in connection with such vesting. Such shares had a market value of $21.86 per share, the closing price of the common stock on the first trading day following the vesting date.</footnote>
        <footnote id="F4">Consists of the number of shares of common stock held by the reporting person as of May 24, 2020 that are not subject to further vesting conditions.</footnote>
        <footnote id="F5">Consists of the total number of shares of common stock underlying restricted stock units held by the reporting person as of May 24, 2020 that remain subject to time-based vesting.</footnote>
        <footnote id="F6">The Options were granted under the Company's 2014 Equity Incentive Plan and are subject to vesting over a four-year period in equal annual installments on each anniversary of the grant date.</footnote>
        <footnote id="F7">The Options were granted under the Company's 2014 Equity Incentive Plan and are subject to vesting over a five-year period in equal annual installments on each anniversary of the grant date.</footnote>
        <footnote id="F8">The Options were granted under the Company's 2014 Equity Incentive Plan and are subject to vesting on May 20, 2023 if (i) with respect to 33% of the shares of common stock issuable upon exercise of the Options, the average closing price of the common stock on the New York Stock Exchange during any consecutive 30 trading days between May 20, 2019 and May 20, 2023 (the &quot;Average Trading Price&quot;) equals or exceeds 150% of the exercise price, (ii) with respect to an additional 33% if the Average Trading Price equals or exceeds 175% of the exercise price and (iii) with respect to an additional 34% if the Average Trading Price equals or exceeds 200% of the exercise price, in each case, subject to earlier vesting in connection with death, disability or a change in control.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ James Grant Conroy</signatureName>
        <signatureDate>2020-05-27</signatureDate>
    </ownerSignature>
</ownershipDocument>
