diff --git a/mercurial/commands.py b/mercurial/commands.py
--- a/mercurial/commands.py
+++ b/mercurial/commands.py
@@ -1486,6 +1486,11 @@ def help_(ui, name=None, with_version=Fa
             helplist(_('list of commands:\n\n'), select)
             return
 
+        # check if it's an invalid alias and display its error if it is
+        if getattr(entry[0], 'badalias', False):
+            entry[0](ui)
+            return
+
         # synopsis
         if len(entry) > 2:
             if entry[2].startswith('hg'):
diff --git a/mercurial/dispatch.py b/mercurial/dispatch.py
--- a/mercurial/dispatch.py
+++ b/mercurial/dispatch.py
@@ -177,6 +177,7 @@ class cmdalias(object):
         self.opts = []
         self.help = ''
         self.norepo = True
+        self.badalias = False
 
         try:
             cmdutil.findcmd(self.name, cmdtable, True)
@@ -189,6 +190,7 @@ class cmdalias(object):
                 ui.warn(_("no definition for alias '%s'\n") % self.name)
                 return 1
             self.fn = fn
+            self.badalias = True
 
             return
 
@@ -217,12 +219,14 @@ class cmdalias(object):
                             % (self.name, cmd))
                 return 1
             self.fn = fn
+            self.badalias = True
         except error.AmbiguousCommand:
             def fn(ui, *args):
                 ui.warn(_("alias '%s' resolves to ambiguous command '%s'\n") \
                             % (self.name, cmd))
                 return 1
             self.fn = fn
+            self.badalias = True
 
     def __call__(self, ui, *args, **opts):
         if self.shadows:
diff --git a/tests/test-alias b/tests/test-alias
--- a/tests/test-alias
+++ b/tests/test-alias
@@ -25,15 +25,19 @@ hg myinit alias
 
 echo '% unknown'
 hg unknown
+hg help unknown
 
 echo '% ambiguous'
 hg ambiguous
+hg help ambiguous
 
 echo '% recursive'
 hg recursive
+hg help recursive
 
 echo '% no definition'
 hg nodef
+hg help nodef
 
 cd alias
 
diff --git a/tests/test-alias.out b/tests/test-alias.out
--- a/tests/test-alias.out
+++ b/tests/test-alias.out
@@ -1,12 +1,16 @@
 % basic
 % unknown
 alias 'unknown' resolves to unknown command 'bargle'
+alias 'unknown' resolves to unknown command 'bargle'
 % ambiguous
 alias 'ambiguous' resolves to ambiguous command 's'
+alias 'ambiguous' resolves to ambiguous command 's'
 % recursive
 alias 'recursive' resolves to unknown command 'recursive'
+alias 'recursive' resolves to unknown command 'recursive'
 % no definition
 no definition for alias 'nodefinition'
+no definition for alias 'nodefinition'
 % no usage
 no rollback information available
 adding foo