diff --git a/Doc/library/pkgutil.rst b/Doc/library/pkgutil.rst
index 5473a367c49a3a..54455d8ab77090 100644
--- a/Doc/library/pkgutil.rst
+++ b/Doc/library/pkgutil.rst
@@ -112,10 +112,17 @@ support.
    *path* should be either ``None`` or a list of paths to look for modules in.
 
    *prefix* is a string to output on the front of every module name on output.
+   It also becomes part of the name under which each package is imported
+   during the recursive descent.
 
    Note that this function must import all *packages* (*not* all modules!) on
    the given *path*, in order to access the ``__path__`` attribute to find
-   submodules.
+   submodules.  The import is done by name, so ``prefix + name`` must resolve
+   to the package that was found on *path*.  If it resolves to a different
+   package, the submodules of that one are listed instead.  If it raises
+   :exc:`ImportError`, the submodules are left out and nothing in the results
+   shows that they are missing.  Passing a package's ``__path__`` together
+   with its ``__name__`` and a trailing dot avoids both.
 
    *onerror* is a function which gets called with one argument (the name of the
    package which was being imported) if any exception occurs while trying to
diff --git a/Lib/pkgutil.py b/Lib/pkgutil.py
index 9121d6a1e2285c..2332d65b937655 100644
--- a/Lib/pkgutil.py
+++ b/Lib/pkgutil.py
@@ -45,11 +45,18 @@ def walk_packages(path=None, prefix='', onerror=None):
     modules in.
 
     'prefix' is a string to output on the front of every module name
-    on output.
+    on output.  It also becomes part of the name under which each
+    package is imported during the recursive descent.
 
     Note that this function must import all *packages* (NOT all
     modules!) on the given path, in order to access the __path__
-    attribute to find submodules.
+    attribute to find submodules.  The import is done by name, so
+    prefix + name must resolve to the package that was found on path.
+    If it resolves to a different package, the submodules of that one
+    are listed instead.  If it raises ImportError, the submodules are
+    left out and nothing in the results shows that they are missing.
+    Passing a package's __path__ together with its __name__ and a
+    trailing dot avoids both.
 
     'onerror' is a function which gets called with one argument (the
     name of the package which was being imported) if any exception
diff --git a/Misc/NEWS.d/next/Documentation/2026-09-25-00-15-48.gh-issue-77391.1utlEd.rst b/Misc/NEWS.d/next/Documentation/2026-09-25-00-15-48.gh-issue-77391.1utlEd.rst
new file mode 100644
index 00000000000000..b7a5eda5cae241
--- /dev/null
+++ b/Misc/NEWS.d/next/Documentation/2026-09-25-00-15-48.gh-issue-77391.1utlEd.rst
@@ -0,0 +1,3 @@
+Document that the *prefix* argument of :func:`pkgutil.walk_packages` affects
+the imports made during the recursive descent, not just the names that are
+returned.