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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2013-11-13</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001396033</issuerCik>
        <issuerName>Lumber Liquidators Holdings, Inc.</issuerName>
        <issuerTradingSymbol>LL</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001251925</rptOwnerCik>
            <rptOwnerName>PRESLEY JOHN M</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>3000 JOHN DEERE ROAD</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>TOANO</rptOwnerCity>
            <rptOwnerState>VA</rptOwnerState>
            <rptOwnerZipCode>23168</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2013-11-13</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>M</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>26385</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>7.58</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>48876</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2013-11-13</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>26385</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>116.5653</value>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>22491</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Stock Option (right to purchase)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>7.58</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2013-11-13</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>M</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>26385</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <value>2016-07-13</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>26385</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">The option was granted on July 13, 2006 and became exercisable one-quarter on each anniversary of the grant date; provided that vesting accelerated by one year upon the issuer's initial public offering.</footnote>
        <footnote id="F2">Weighted sale price for prices ranging from $116.40 to $117.10 per share.  95 shares were sold at $116.65 per share; 100 shares were sold at each of the following prices: $116.69, $116.72, $116.77, $116.80, $117.04, $117.06, $117.07 and $117.10; 121 shares were sold at $116.45 per share; 200 shares were sold at each of the following prices:  $116.67, $116.68 and $116.78; 205 shares were sold at $116.52 per share; 208 shares were sold at $116.87 per share; 292 shares were sold at $116.86 per share; 300 shares were sold at each of the following prices:$116.40 and $116.88; 313 shares were sold at $116.64 per share; 322 shares were sold at $116.66 per share; 400 shares were sold at $116.49 per share; 400 shares were sold at $116.96 per share; 434 shares were sold at $116.44 per share; 500 shares were sold at $116.51 per share; 506 shares were sold at $116.48 per share; 595 shares were sold at $116.54 per share; 694 shares were sold at $116.47 per share (continued in Footnote 2).</footnote>
        <footnote id="F3">(Continued from Footnote 1) 700 shares were sold at $116.57 per share; 700 shares were sold at $116.73 per share; 708 shares were sold at $116.63 per share; 720 shares were sold at $116.55 per share; 752 shares were sold at $116.61 per share; 900 shares were sold at $116.56 per share; 902 shares were sold at $116.59 per share; 1,100 shares were sold at $116.58 per share; 1,251 shares were sold at $116.42 per share; 1,530 shares were sold at $116.43 per share; 1,692 shares were sold at $116.62 per share; 1,700 shares were sold at $116.53 per share; 1,885 shares were sold at $116.50 per share; 2,219 shares were sold at $116.41 per share; and 2,541 shares were sold at $116.60 per share.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ E. Livingston B. Haskell, Power-of-Attorney</signatureName>
        <signatureDate>2013-11-14</signatureDate>
    </ownerSignature>
</ownershipDocument>
