diff --git a/README.md b/README.md
index f2cd53b..c6c7d22 100644
--- a/README.md
+++ b/README.md
@@ -43,6 +43,23 @@ than most of your human colleagues 😏
 4. Copy the `Bot User OAuth Access Token` and add it to your environment as `SLACK_BOT_TOKEN`.
 5. Create a new `App-Level Tokens` under `Basic Infomation` and add it to your environment as `SLACK_APP_TOKEN`.
 
+### User Whitelisting (Optional)
+
+Sam supports user whitelisting to restrict who can interact with the bot. This is useful for controlling access in larger Slack workspaces.
+
+To enable whitelisting:
+1. Add the `WHITELISTED_USERS` environment variable to your `.env` file
+2. Set it to a comma-separated list of Slack user IDs
+3. Example: `WHITELISTED_USERS=U1234567890,U0987654321,U1122334455`
+
+**Finding Slack User IDs:**
+- In Slack, click on a user's profile
+- Click "More" → "Copy member ID"
+- Or use the format from user mentions in Slack (the part after `@`)
+
+If `WHITELISTED_USERS` is empty or not set, all users can interact with Sam (default behavior).
+
+When a non-whitelisted user tries to interact with Sam, the bot will silently ignore their messages.
 
 ### How it works
 
diff --git a/sam/config.py b/sam/config.py
index 0a22377..e9747f3 100644
--- a/sam/config.py
+++ b/sam/config.py
@@ -41,6 +41,10 @@
 SLACK_BOT_TOKEN: str = os.getenv("SLACK_BOT_TOKEN")
 #: The Slack app token, prefixed with `xapp-`.
 SLACK_APP_TOKEN: str = os.getenv("SLACK_APP_TOKEN")
+#: Comma-separated list of Slack user IDs allowed to interact with the bot. If empty, all users are allowed.
+WHITELISTED_USERS: list[str] = [
+    user.strip() for user in os.getenv("WHITELISTED_USERS", "").split(",") if user.strip()
+]
 
 # Sentry
 #: The Sentry DSN for Sentry based error reporting.
diff --git a/sam/slack.py b/sam/slack.py
index da2f6cf..555fe65 100644
--- a/sam/slack.py
+++ b/sam/slack.py
@@ -55,6 +55,13 @@ async def handle_message(event: {str, Any}, say: AsyncSay):
     if event.get("subtype") in ["message_changed", "message_deleted"]:
         logger.debug("Ignoring `%s` event", event["subtype"])
         return
+    
+    # Check if user is whitelisted (if whitelist is configured)
+    user_id = event.get("user")
+    if config.WHITELISTED_USERS and user_id not in config.WHITELISTED_USERS:
+        logger.debug("Ignoring message from non-whitelisted user: %s", user_id)
+        return
+    
     bot_id = await get_bot_user_id()
     channel_id = event["channel"]
     channel_type = event["channel_type"]
@@ -103,9 +110,14 @@ async def send_response(
     voice_response: bool = False,
 ):
     """Send a response to a message event from Slack."""
+    # Check if user is whitelisted (if whitelist is configured)
+    user_id = event["user"]
+    if config.WHITELISTED_USERS and user_id not in config.WHITELISTED_USERS:
+        logger.debug("Ignoring response request from non-whitelisted user: %s", user_id)
+        return
+    
     logger.debug("process_run=%s", json.dumps(event))
     channel_id = event["channel"]
-    user_id = event["user"]
     try:
         timestamp = event["ts"]
     except KeyError:
diff --git a/template.env b/template.env
index 62a9fa2..1237b97 100644
--- a/template.env
+++ b/template.env
@@ -5,3 +5,4 @@ SLACK_APP_TOKEN=
 SLACK_BOT_TOKEN=
 OPENAI_API_KEY=
 REDIS_URL=redis://redis:6379/1
+WHITELISTED_USERS=