diff --git a/Doc/library/argparse.rst b/Doc/library/argparse.rst
index db5fae2006678a..23538c22a8d6f6 100644
--- a/Doc/library/argparse.rst
+++ b/Doc/library/argparse.rst
@@ -1369,6 +1369,11 @@ behavior::
    >>> parser.parse_args('--foo XXX'.split())
    Namespace(bar='XXX')
 
+Multiple arguments may share the same ``dest``.  By default, the value from the
+last such argument given on the command line wins.  Use ``action='append'`` to
+collect values from all of them into a list instead.  For conflicting *option
+strings* rather than ``dest`` names, see conflict_handler_.
+
 .. versionchanged:: 3.15
    Single-dash long option now takes precedence over short options.
 
@@ -1777,6 +1782,10 @@ Subcommands
    present, and when the ``b`` command is specified, only the ``foo`` and
    ``baz`` attributes are present.
 
+   If a subparser defines an argument with the same ``dest`` as the parent
+   parser, the subparser's value overwrites the parent's, so users should give
+   them distinct ``dest`` values to keep both.
+
    Similarly, when a help message is requested from a subparser, only the help
    for that particular parser will be printed.  The help message will not
    include parent parser or sibling parser messages.  (A help message for each