diff --git a/README.md b/README.md
index 33cdeee..6c9304d 100644
--- a/README.md
+++ b/README.md
@@ -293,12 +293,18 @@ If you prefer to configure manually, add the following to `~/.nanobot/config.jso
     "discord": {
       "enabled": true,
       "token": "YOUR_BOT_TOKEN",
-      "allowFrom": ["YOUR_USER_ID"]
+      "allowFrom": ["YOUR_USER_ID"],
+      "groupPolicy": "mention"
     }
   }
 }
 ```
 
+> `groupPolicy` controls how the bot responds in group channels:
+> - `"mention"` (default) — Only respond when @mentioned
+> - `"open"` — Respond to all messages
+> DMs always respond when the sender is in `allowFrom`.
+
 **5. Invite the bot**
 - OAuth2 → URL Generator
 - Scopes: `bot`
diff --git a/nanobot/channels/discord.py b/nanobot/channels/discord.py
index 57e5922..900c17b 100644
--- a/nanobot/channels/discord.py
+++ b/nanobot/channels/discord.py
@@ -54,6 +54,7 @@ class DiscordChannel(BaseChannel):
         self._heartbeat_task: asyncio.Task | None = None
         self._typing_tasks: dict[str, asyncio.Task] = {}
         self._http: httpx.AsyncClient | None = None
+        self._bot_user_id: str | None = None
 
     async def start(self) -> None:
         """Start the Discord gateway connection."""
@@ -170,6 +171,10 @@ class DiscordChannel(BaseChannel):
                 await self._identify()
             elif op == 0 and event_type == "READY":
                 logger.info("Discord gateway READY")
+                # Capture bot user ID for mention detection
+                user_data = payload.get("user") or {}
+                self._bot_user_id = user_data.get("id")
+                logger.info("Discord bot connected as user {}", self._bot_user_id)
             elif op == 0 and event_type == "MESSAGE_CREATE":
                 await self._handle_message_create(payload)
             elif op == 7:
@@ -226,6 +231,7 @@ class DiscordChannel(BaseChannel):
         sender_id = str(author.get("id", ""))
         channel_id = str(payload.get("channel_id", ""))
         content = payload.get("content") or ""
+        guild_id = payload.get("guild_id")
 
         if not sender_id or not channel_id:
             return
@@ -233,6 +239,11 @@ class DiscordChannel(BaseChannel):
         if not self.is_allowed(sender_id):
             return
 
+        # Check group channel policy (DMs always respond if is_allowed passes)
+        if guild_id is not None:
+            if not self._should_respond_in_group(payload, content):
+                return
+
         content_parts = [content] if content else []
         media_paths: list[str] = []
         media_dir = Path.home() / ".nanobot" / "media"
@@ -269,11 +280,32 @@ class DiscordChannel(BaseChannel):
             media=media_paths,
             metadata={
                 "message_id": str(payload.get("id", "")),
-                "guild_id": payload.get("guild_id"),
+                "guild_id": guild_id,
                 "reply_to": reply_to,
             },
         )
 
+    def _should_respond_in_group(self, payload: dict[str, Any], content: str) -> bool:
+        """Check if bot should respond in a group channel based on policy."""
+        if self.config.group_policy == "open":
+            return True
+
+        if self.config.group_policy == "mention":
+            # Check if bot was mentioned in the message
+            if self._bot_user_id:
+                # Check mentions array
+                mentions = payload.get("mentions") or []
+                for mention in mentions:
+                    if str(mention.get("id")) == self._bot_user_id:
+                        return True
+                # Also check content for mention format <@USER_ID>
+                if f"<@{self._bot_user_id}>" in content or f"<@!{self._bot_user_id}>" in content:
+                    return True
+            logger.debug("Discord message in {} ignored (bot not mentioned)", payload.get("channel_id"))
+            return False
+
+        return True
+
     async def _start_typing(self, channel_id: str) -> None:
         """Start periodic typing indicator for a channel."""
         await self._stop_typing(channel_id)
diff --git a/nanobot/config/schema.py b/nanobot/config/schema.py
index 61a7bd2..9d7da3b 100644
--- a/nanobot/config/schema.py
+++ b/nanobot/config/schema.py
@@ -62,6 +62,7 @@ class DiscordConfig(Base):
     allow_from: list[str] = Field(default_factory=list)  # Allowed user IDs
     gateway_url: str = "wss://gateway.discord.gg/?v=10&encoding=json"
     intents: int = 37377  # GUILDS + GUILD_MESSAGES + DIRECT_MESSAGES + MESSAGE_CONTENT
+    group_policy: Literal["mention", "open"] = "mention"
 
 
 class MatrixConfig(Base):