diff --git a/python/mach/mach/base.py b/python/mach/mach/base.py
index 7f6674f5a9f..b2ef404191e 100644
--- a/python/mach/mach/base.py
+++ b/python/mach/mach/base.py
@@ -80,13 +80,17 @@ class MethodHandler(object):
         # in a given context.
         'conditions',
 
+        # argparse.ArgumentParser instance to use as the basis for command
+        # arguments.
+        'parser',
+
         # Arguments added to this command's parser. This is a 2-tuple of
         # positional and named arguments, respectively.
         'arguments',
     )
 
     def __init__(self, cls, method, name, category=None, description=None,
-        allow_all_arguments=False, conditions=None, arguments=None,
+        allow_all_arguments=False, conditions=None, parser=None, arguments=None,
         pass_context=False):
 
         self.cls = cls
@@ -96,6 +100,7 @@ class MethodHandler(object):
         self.description = description
         self.allow_all_arguments = allow_all_arguments
         self.conditions = conditions or []
+        self.parser = parser
         self.arguments = arguments or []
         self.pass_context = pass_context
 
diff --git a/python/mach/mach/decorators.py b/python/mach/mach/decorators.py
index 8889f28dd77..cb9a67428e7 100644
--- a/python/mach/mach/decorators.py
+++ b/python/mach/mach/decorators.py
@@ -56,8 +56,8 @@ def CommandProvider(cls):
         if not isinstance(value, types.FunctionType):
             continue
 
-        command_name, category, description, allow_all, conditions = getattr(
-            value, '_mach_command', (None, None, None, None, None))
+        command_name, category, description, allow_all, conditions, parser = getattr(
+            value, '_mach_command', (None, None, None, None, None, None))
 
         if command_name is None:
             continue
@@ -83,7 +83,7 @@ def CommandProvider(cls):
 
         handler = MethodHandler(cls, attr, command_name, category=category,
             description=description, allow_all_arguments=allow_all,
-            conditions=conditions, arguments=arguments,
+            conditions=conditions, parser=parser, arguments=arguments,
             pass_context=pass_context)
 
         Registrar.register_command_handler(handler)
@@ -105,6 +105,9 @@ class Command(object):
          allow_all_args -- Bool indicating whether to allow unknown arguments
              through to the command.
 
+         parser -- an optional argparse.ArgumentParser instance to use as
+             the basis for the command arguments.
+
     For example:
 
         @Command('foo', category='misc', description='Run the foo action')
@@ -112,16 +115,17 @@ class Command(object):
             pass
     """
     def __init__(self, name, category=None, description=None,
-        allow_all_args=False, conditions=None):
+                 allow_all_args=False, conditions=None, parser=None):
         self._name = name
         self._category = category
         self._description = description
         self._allow_all_args = allow_all_args
         self._conditions = conditions
+        self._parser = parser
 
     def __call__(self, func):
         func._mach_command = (self._name, self._category, self._description,
-            self._allow_all_args, self._conditions)
+                              self._allow_all_args, self._conditions, self._parser)
 
         return func
 
diff --git a/python/mach/mach/dispatcher.py b/python/mach/mach/dispatcher.py
index 5ac3a37d7b4..e15bf75201c 100644
--- a/python/mach/mach/dispatcher.py
+++ b/python/mach/mach/dispatcher.py
@@ -123,7 +123,10 @@ class CommandAction(argparse.Action):
         if handler.allow_all_arguments:
             parser_args['prefix_chars'] = '+'
 
-        subparser = argparse.ArgumentParser(**parser_args)
+        if handler.parser:
+            subparser = handler.parser
+        else:
+            subparser = argparse.ArgumentParser(**parser_args)
 
         for arg in handler.arguments:
             subparser.add_argument(*arg[0], **arg[1])
@@ -216,9 +219,25 @@ class CommandAction(argparse.Action):
         if handler.allow_all_arguments:
             parser_args['prefix_chars'] = '+'
 
-        c_parser = argparse.ArgumentParser(**parser_args)
-
-        group = c_parser.add_argument_group('Command Arguments')
+        if handler.parser:
+            c_parser = handler.parser
+            c_parser.formatter_class = NoUsageFormatter
+            try:
+                # By default argparse adds two groups called "positional arguments"
+                # and "optional arguments". We want to rename these to reflect standard
+                # mach terminology.
+                c_parser._action_groups[0].title = 'Command Parameters'
+                c_parser._action_groups[1].title = 'Command Arguments'
+            except:
+                # If argparse changes the internal data structures here continue;
+                # this will just make the output more ugly
+                pass
+            if not handler.description:
+                handler.description = c_parser.description
+                c_parser.description = None
+        else:
+            c_parser = argparse.ArgumentParser(**parser_args)
+            group = c_parser.add_argument_group('Command Arguments')
 
         for arg in handler.arguments:
             group.add_argument(*arg[0], **arg[1])
@@ -234,3 +253,6 @@ class CommandAction(argparse.Action):
         print('')
         c_parser.print_help()
 
+class NoUsageFormatter(argparse.HelpFormatter):
+    def _format_usage(self, *args, **kwargs):
+        return ""