diff --git a/docs/pages/pmd/userdocs/cli_reference.md b/docs/pages/pmd/userdocs/cli_reference.md
index ba0353d144..19f5ad547e 100644
--- a/docs/pages/pmd/userdocs/cli_reference.md
+++ b/docs/pages/pmd/userdocs/cli_reference.md
@@ -194,6 +194,21 @@ Just set the environment variable `PMD_JAVA_OPTS` before executing PMD, e.g.
    windows="set \"PMD_JAVA_OPTS=--enable-preview\"
     pmd.bat check -d src\main\java\ -f text -R rulesets/java/quickstart.xml" %}
 
+## Additional runtime classpath
+
+If you develop custom rules and package them as a jar file, you need to add it to PMD's runtime classpath.
+You can either copy the jar file into the `lib/` subfolder alongside the other jar files, that are in PMD's
+standard distribution.
+
+Or you can set the environment variable `CLASSPATH` before starting PMD, e.g.
+
+{% include cli_example.html
+   id="preview_classpath"
+   linux="export CLASSPATH=custom-rule-example.jar
+    pmd check -d ../../../src/main/java/ -f text -R myrule.xml"
+   windows="set CLASSPATH=custom-rule-example.jar
+    pmd.bat check -d ..\..\..\src\main\java\ -f text -R myrule.xml" %}
+
 ## Exit Status
 
 Please note that if PMD detects any violations, it will exit with status 4 (since 5.3).
diff --git a/docs/pages/release_notes.md b/docs/pages/release_notes.md
index e917abee1b..55fc00125a 100644
--- a/docs/pages/release_notes.md
+++ b/docs/pages/release_notes.md
@@ -29,6 +29,8 @@ Being based on a proper Antlr grammar, CPD can:
 * honor [comment-based suppressions](pmd_userdocs_cpd.html#suppression)
 
 ### Fixed Issues
+* core
+  * [#4395](https://github.com/pmd/pmd/issues/4395): \[core] Support environment variable CLASSPATH with pmd.bat under Windows
 * java-errorprone
   * [#4393](https://github.com/pmd/pmd/issues/4393): \[java] MissingStaticMethodInNonInstantiatableClass false-positive for Lombok's @UtilityClass for classes with non-private fields
 
diff --git a/pmd-dist/src/main/resources/scripts/pmd.bat b/pmd-dist/src/main/resources/scripts/pmd.bat
index 9c5b3cdf75..f7d3fe9474 100644
--- a/pmd-dist/src/main/resources/scripts/pmd.bat
+++ b/pmd-dist/src/main/resources/scripts/pmd.bat
@@ -63,10 +63,15 @@ if %_needjfxlib% EQU 1 (
     )
     :: The wildcard will include only jar files, but we need to access also
     :: property files such as javafx.properties that lay bare in the dir
-    set classpath=%TOPDIR%\conf;%TOPDIR%\lib\*;%JAVAFX_HOME%\lib\*;%JAVAFX_HOME%\lib\
+    set pmd_classpath=%TOPDIR%\conf;%TOPDIR%\lib\*;%JAVAFX_HOME%\lib\*;%JAVAFX_HOME%\lib\
 ) else (
-    set classpath=%TOPDIR%\conf;%TOPDIR%\lib\*
+    set pmd_classpath=%TOPDIR%\conf;%TOPDIR%\lib\*
 )
 
+if [%CLASSPATH%] NEQ [] (
+    set classpath=%CLASSPATH%;%pmd_classpath%
+) else (
+    set classpath=%pmd_classpath%
+)
 
-java %PMD_JAVA_OPTS% %jreopts% -classpath %classpath% %OPTS% %MAIN_CLASS% %*
+java %PMD_JAVA_OPTS% %jreopts% -classpath %pmd_classpath% %OPTS% %MAIN_CLASS% %*