<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2026 Workiva-->
<!--r:019f146f-ff7a-7fd9-90a5-8182959dc3d0,g:1e375500-9106-4297-8e0c-29ab502d79bc-->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:roleRef roleURI="http://praxismedicines.com/role/Cover" xlink:type="simple" xlink:href="prax-20260629.xsd#Cover"/>
  <link:presentationLink xlink:role="http://praxismedicines.com/role/Cover" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_dei_CoverAbstract_019f146f-ff7a-7bb9-99f9-de3211db89e3" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_CoverAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentType_019f146f-ff7a-75f1-8842-fe4be4b2d306" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentType"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019f146f-ff7a-7bb9-99f9-de3211db89e3" xlink:to="loc_dei_DocumentType_019f146f-ff7a-75f1-8842-fe4be4b2d306" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentPeriodEndDate_019f146f-ff7a-7cf5-b3f0-7f90404d2e77" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentPeriodEndDate"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019f146f-ff7a-7bb9-99f9-de3211db89e3" xlink:to="loc_dei_DocumentPeriodEndDate_019f146f-ff7a-7cf5-b3f0-7f90404d2e77" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityRegistrantName_019f146f-ff7a-7df0-b906-afb16d7685bf" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityRegistrantName"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019f146f-ff7a-7bb9-99f9-de3211db89e3" xlink:to="loc_dei_EntityRegistrantName_019f146f-ff7a-7df0-b906-afb16d7685bf" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_AmendmentFlag_019f146f-ff7a-75c8-806c-f4e7e73b5c02" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_AmendmentFlag"/>
    <link:presentationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019f146f-ff7a-7bb9-99f9-de3211db89e3" xlink:to="loc_dei_AmendmentFlag_019f146f-ff7a-75c8-806c-f4e7e73b5c02" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCentralIndexKey_019f146f-ff7a-79bb-9044-49fbb950a234" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityCentralIndexKey"/>
    <link:presentationArc order="5" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019f146f-ff7a-7bb9-99f9-de3211db89e3" xlink:to="loc_dei_EntityCentralIndexKey_019f146f-ff7a-79bb-9044-49fbb950a234" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityIncorporationStateCountryCode_019f146f-ff7a-708d-8587-79c6490a1a87" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityIncorporationStateCountryCode"/>
    <link:presentationArc order="6" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019f146f-ff7a-7bb9-99f9-de3211db89e3" xlink:to="loc_dei_EntityIncorporationStateCountryCode_019f146f-ff7a-708d-8587-79c6490a1a87" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFileNumber_019f146f-ff7a-78ec-a081-d2da166589d9" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityFileNumber"/>
    <link:presentationArc order="7" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019f146f-ff7a-7bb9-99f9-de3211db89e3" xlink:to="loc_dei_EntityFileNumber_019f146f-ff7a-78ec-a081-d2da166589d9" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityTaxIdentificationNumber_019f146f-ff7a-7fa6-b2f0-df7aa17848c8" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityTaxIdentificationNumber"/>
    <link:presentationArc order="8" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019f146f-ff7a-7bb9-99f9-de3211db89e3" xlink:to="loc_dei_EntityTaxIdentificationNumber_019f146f-ff7a-7fa6-b2f0-df7aa17848c8" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine1_019f146f-ff7a-74d2-a652-d33ce42532ff" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressAddressLine1"/>
    <link:presentationArc order="9" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019f146f-ff7a-7bb9-99f9-de3211db89e3" xlink:to="loc_dei_EntityAddressAddressLine1_019f146f-ff7a-74d2-a652-d33ce42532ff" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine2_019f146f-ff7a-756c-b600-55555b77fdbc" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressAddressLine2"/>
    <link:presentationArc order="10" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019f146f-ff7a-7bb9-99f9-de3211db89e3" xlink:to="loc_dei_EntityAddressAddressLine2_019f146f-ff7a-756c-b600-55555b77fdbc" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressCityOrTown_019f146f-ff7a-7460-b6c2-64ff0e08530c" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressCityOrTown"/>
    <link:presentationArc order="11" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019f146f-ff7a-7bb9-99f9-de3211db89e3" xlink:to="loc_dei_EntityAddressCityOrTown_019f146f-ff7a-7460-b6c2-64ff0e08530c" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressStateOrProvince_019f146f-ff7a-717b-a4e3-afc374df7243" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressStateOrProvince"/>
    <link:presentationArc order="12" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019f146f-ff7a-7bb9-99f9-de3211db89e3" xlink:to="loc_dei_EntityAddressStateOrProvince_019f146f-ff7a-717b-a4e3-afc374df7243" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressPostalZipCode_019f146f-ff7a-73b3-86f8-bc0a49e6b821" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressPostalZipCode"/>
    <link:presentationArc order="13" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019f146f-ff7a-7bb9-99f9-de3211db89e3" xlink:to="loc_dei_EntityAddressPostalZipCode_019f146f-ff7a-73b3-86f8-bc0a49e6b821" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CityAreaCode_019f146f-ff7a-73a9-a6cc-28af6f003ec7" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_CityAreaCode"/>
    <link:presentationArc order="14" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019f146f-ff7a-7bb9-99f9-de3211db89e3" xlink:to="loc_dei_CityAreaCode_019f146f-ff7a-73a9-a6cc-28af6f003ec7" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LocalPhoneNumber_019f146f-ff7a-7752-9209-f26bbfedecdd" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_LocalPhoneNumber"/>
    <link:presentationArc order="15" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019f146f-ff7a-7bb9-99f9-de3211db89e3" xlink:to="loc_dei_LocalPhoneNumber_019f146f-ff7a-7752-9209-f26bbfedecdd" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_WrittenCommunications_019f146f-ff7a-7538-a09b-cfc9cc7e58ac" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_WrittenCommunications"/>
    <link:presentationArc order="16" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019f146f-ff7a-7bb9-99f9-de3211db89e3" xlink:to="loc_dei_WrittenCommunications_019f146f-ff7a-7538-a09b-cfc9cc7e58ac" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_SolicitingMaterial_019f146f-ff7a-7572-800d-35d467105eba" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_SolicitingMaterial"/>
    <link:presentationArc order="17" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019f146f-ff7a-7bb9-99f9-de3211db89e3" xlink:to="loc_dei_SolicitingMaterial_019f146f-ff7a-7572-800d-35d467105eba" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_PreCommencementTenderOffer_019f146f-ff7a-77fb-9a37-b03ce3b4133a" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_PreCommencementTenderOffer"/>
    <link:presentationArc order="18" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019f146f-ff7a-7bb9-99f9-de3211db89e3" xlink:to="loc_dei_PreCommencementTenderOffer_019f146f-ff7a-77fb-9a37-b03ce3b4133a" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_PreCommencementIssuerTenderOffer_019f146f-ff7a-7c96-81b7-d3389044094a" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_PreCommencementIssuerTenderOffer"/>
    <link:presentationArc order="19" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019f146f-ff7a-7bb9-99f9-de3211db89e3" xlink:to="loc_dei_PreCommencementIssuerTenderOffer_019f146f-ff7a-7c96-81b7-d3389044094a" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_Security12bTitle_019f146f-ff7a-7474-8427-4686a78f0c87" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_Security12bTitle"/>
    <link:presentationArc order="20" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019f146f-ff7a-7bb9-99f9-de3211db89e3" xlink:to="loc_dei_Security12bTitle_019f146f-ff7a-7474-8427-4686a78f0c87" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_TradingSymbol_019f146f-ff7a-7f8a-8aab-e98915838a07" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_TradingSymbol"/>
    <link:presentationArc order="21" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019f146f-ff7a-7bb9-99f9-de3211db89e3" xlink:to="loc_dei_TradingSymbol_019f146f-ff7a-7f8a-8aab-e98915838a07" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_SecurityExchangeName_019f146f-ff7a-7185-bc09-3ef33561370f" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_SecurityExchangeName"/>
    <link:presentationArc order="22" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019f146f-ff7a-7bb9-99f9-de3211db89e3" xlink:to="loc_dei_SecurityExchangeName_019f146f-ff7a-7185-bc09-3ef33561370f" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityEmergingGrowthCompany_019f146f-ff7a-7e7d-ac64-fcedfde6cde1" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityEmergingGrowthCompany"/>
    <link:presentationArc order="23" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019f146f-ff7a-7bb9-99f9-de3211db89e3" xlink:to="loc_dei_EntityEmergingGrowthCompany_019f146f-ff7a-7e7d-ac64-fcedfde6cde1" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
  </link:presentationLink>
</link:linkbase>
