diff --git a/discord/app/commands.py b/discord/app/commands.py
index 832d7d0496..27f15de099 100644
--- a/discord/app/commands.py
+++ b/discord/app/commands.py
@@ -36,7 +36,7 @@
 from ..message import Message
 from .context import InteractionContext
 from ..utils import find, get_or_fetch
-
+from ..errors import NotFound
 
 class ApplicationCommand:
     def __repr__(self):
@@ -88,7 +88,7 @@ def __init__(self, func: Callable, *args, **kwargs) -> None:
         for a, o in options.items():
             o = o.annotation
             if not isinstance(o, Option):
-                o = Option(o, 'No description provided')
+                o = Option(o, "No description provided")
             if o.name is None:
                 o.name = a
             self.options.append(o)
@@ -128,7 +128,12 @@ async def invoke(self, interaction) -> None:
             ):
                 arg = await get_or_fetch(ctx.guild, op.input_type.name, int(arg))
 
-            # TODO: Add discord.Mentionable
+            elif op.input_type == SlashCommandOptionType.mentionable:
+                try:
+                    arg = await get_or_fetch(ctx.guild, "member", int(arg))
+                except NotFound: 
+                    arg = await get_or_fetch(ctx.guild, "role", int(arg))
+
             final_args.append(arg)
 
         await self.callback(ctx, *final_args)
diff --git a/discord/app/context.py b/discord/app/context.py
index d903707ae2..846b983a4e 100644
--- a/discord/app/context.py
+++ b/discord/app/context.py
@@ -25,6 +25,7 @@
 from ..interactions import Interaction
 from ..utils import cached_property
 
+
 class InteractionContext:
     def __init__(self, interaction: Interaction):
         self.interaction = interaction
@@ -59,4 +60,4 @@ def respond(self):
 
     @property
     def defer(self):
-        return self.interaction.response.defer
\ No newline at end of file
+        return self.interaction.response.defer