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

    <schemaVersion>X0206</schemaVersion>

    <documentType>3</documentType>

    <periodOfReport>2020-09-27</periodOfReport>

    <noSecuritiesOwned>0</noSecuritiesOwned>

    <issuer>
        <issuerCik>0000893949</issuerCik>
        <issuerName>MEDNAX, INC.</issuerName>
        <issuerTradingSymbol>MD</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001826596</rptOwnerCik>
            <rptOwnerName>Hinson Roger Mack</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>1301 CONCORD TERRACE</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>SUNRISE</rptOwnerCity>
            <rptOwnerState>FL</rptOwnerState>
            <rptOwnerZipCode>33323</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Pres., PDX &amp; OBX Medical Group</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>53358</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>16279</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeHolding>
            <securityTitle>
                <value>Employee Stock Option (right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>16.14</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2021-09-26</value>
                <footnoteId id="F3"/>
            </exerciseDate>
            <expirationDate>
                <value>2023-12-26</value>
                <footnoteId id="F3"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>144000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Includes an aggregate of 480 shares of the Issuer's common stock (&quot;Common Stock&quot;) acquired to date under the Issuer's 1996 Non-Qualified Employee Stock Purchase Plan, as amended.  Also includes an aggregate of 44,663 restricted shares of Common Stock granted pursuant to the Issuer's Amended and Restated 2008 Incentive Compensation Plan (the &quot;2008 Plan&quot;), of which (i) 10,201 shares will vest on March 1, 2021, (ii) 1,934 shares will vest on March 1, 2022, (iii) 16,264 shares will vest on September 26, 2022 and (iv) 16,264 shares will vest on September 26, 2023, in each case subject to the terms of the 2008 Plan.</footnote>
        <footnote id="F2">Restricted shares of Common Stock granted pursuant to the 2008 Plan in connection with annual equity award. The number of shares being reported represents the &quot;target&quot; number of restricted shares and does not include the right of the reporting person to receive up to 4,070 additional shares based on the achievement of certain performance-based criteria for the twelve months ending December 31, 2020. The actual number of shares earned could be less than or greater than the target number, depending on the level of performance achieved, and all of the restricted shares granted are subject to forfeiture if minimum levels of performance are not met. Any restricted shares earned will not vest any earlier than in three equal installments on March 1, 2021, March 1, 2022 and March 1, 2023, subject to the terms of the 2008 Plan.</footnote>
        <footnote id="F3">Option to purchase shares of Common Stock granted pursuant to the 2008 Plan that vests as follows: (A) 46,000 shares are exercisable if and when the Common Stock price closes at $22 per share (or above) for any 40 consecutive trading days before the third anniversary of the grant date (&quot;Performance End Date&quot;); (B) 47,500 shares are exercisable if and when the Common Stock price closes at $25 per share (or above) for any 40 consecutive trading days before the Performance End Date; and (C) 50,500 of the option shares are exercisable if and when the Common Stock price closes at $29 per share (or above) for any 40 consecutive trading days before the Performance End Date; provided, that no option shares will vest prior to the one-year anniversary of the grant date.</footnote>
    </footnotes>

    <remarks>Exhibit 24 - Power of Attorney</remarks>

    <ownerSignature>
        <signatureName>/s/ Dominic J. Andreano, Attorney-in-Fact</signatureName>
        <signatureDate>2020-09-29</signatureDate>
    </ownerSignature>
</ownershipDocument>
