diff --git a/src/pipecat/processors/filters/stt_mute_filter.py b/src/pipecat/processors/filters/stt_mute_filter.py
index fcd492bb3..a5430a451 100644
--- a/src/pipecat/processors/filters/stt_mute_filter.py
+++ b/src/pipecat/processors/filters/stt_mute_filter.py
@@ -23,6 +23,7 @@ from pipecat.frames.frames import (
     Frame,
     FunctionCallInProgressFrame,
     FunctionCallResultFrame,
+    StartFrame,
     StartInterruptionFrame,
     StopInterruptionFrame,
     STTMuteFrame,
@@ -108,7 +109,7 @@ class STTMuteFilter(FrameProcessor):
         self._first_speech_handled = False
         self._bot_is_speaking = False
         self._function_call_in_progress = False
-        self._is_muted = STTMuteStrategy.MUTE_UNTIL_FIRST_BOT_COMPLETE in self._config.strategies
+        self._is_muted = False  # Initialize as unmuted, will set state on StartFrame if needed
 
     @property
     def is_muted(self) -> bool:
@@ -155,6 +156,13 @@ class STTMuteFilter(FrameProcessor):
         """Processes incoming frames and manages muting state."""
         await super().process_frame(frame, direction)
 
+        # Handle initial state on StartFrame
+        if isinstance(frame, StartFrame):
+            # Check if we should start muted
+            should_mute = await self._should_mute()
+            if should_mute:
+                await self._handle_mute_state(True)
+
         # First determine if we need to change mute state
         should_mute = None
 
diff --git a/tests/test_stt_mute_filter.py b/tests/test_stt_mute_filter.py
new file mode 100644
index 000000000..62bdd03c9
--- /dev/null
+++ b/tests/test_stt_mute_filter.py
@@ -0,0 +1,217 @@
+#
+# Copyright (c) 2024-2025 Daily
+#
+# SPDX-License-Identifier: BSD 2-Clause License
+#
+
+import unittest
+
+from pipecat.frames.frames import (
+    BotStartedSpeakingFrame,
+    BotStoppedSpeakingFrame,
+    FunctionCallInProgressFrame,
+    FunctionCallResultFrame,
+    STTMuteFrame,
+    UserStartedSpeakingFrame,
+    UserStoppedSpeakingFrame,
+)
+from pipecat.processors.filters.stt_mute_filter import STTMuteConfig, STTMuteFilter, STTMuteStrategy
+from pipecat.tests.utils import run_test
+
+
+class TestSTTMuteFilter(unittest.IsolatedAsyncioTestCase):
+    async def test_first_speech_strategy(self):
+        filter = STTMuteFilter(config=STTMuteConfig(strategies={STTMuteStrategy.FIRST_SPEECH}))
+
+        frames_to_send = [
+            BotStartedSpeakingFrame(),  # First bot speech starts
+            UserStartedSpeakingFrame(),  # Should be suppressed
+            UserStoppedSpeakingFrame(),  # Should be suppressed
+            BotStoppedSpeakingFrame(),  # First bot speech ends
+            BotStartedSpeakingFrame(),  # Second bot speech
+            UserStartedSpeakingFrame(),  # Should pass through
+            UserStoppedSpeakingFrame(),  # Should pass through
+            BotStoppedSpeakingFrame(),
+        ]
+
+        expected_returned_frames = [
+            BotStartedSpeakingFrame,
+            STTMuteFrame,  # mute=True
+            BotStoppedSpeakingFrame,
+            STTMuteFrame,  # mute=False
+            BotStartedSpeakingFrame,
+            UserStartedSpeakingFrame,  # Now passes through
+            UserStoppedSpeakingFrame,  # Now passes through
+            BotStoppedSpeakingFrame,
+        ]
+
+        await run_test(
+            filter,
+            frames_to_send=frames_to_send,
+            expected_down_frames=expected_returned_frames,
+        )
+
+    async def test_always_strategy(self):
+        filter = STTMuteFilter(config=STTMuteConfig(strategies={STTMuteStrategy.ALWAYS}))
+
+        frames_to_send = [
+            BotStartedSpeakingFrame(),  # First speech starts
+            UserStartedSpeakingFrame(),  # Should be suppressed
+            UserStoppedSpeakingFrame(),  # Should be suppressed
+            BotStoppedSpeakingFrame(),  # First speech ends
+            UserStartedSpeakingFrame(),  # Should pass through
+            UserStoppedSpeakingFrame(),  # Should pass through
+            BotStartedSpeakingFrame(),  # Second speech starts
+            UserStartedSpeakingFrame(),  # Should be suppressed again
+            UserStoppedSpeakingFrame(),  # Should be suppressed again
+            BotStoppedSpeakingFrame(),  # Second speech ends
+        ]
+
+        expected_returned_frames = [
+            BotStartedSpeakingFrame,
+            STTMuteFrame,  # mute=True
+            BotStoppedSpeakingFrame,
+            STTMuteFrame,  # mute=False
+            UserStartedSpeakingFrame,
+            UserStoppedSpeakingFrame,
+            BotStartedSpeakingFrame,
+            STTMuteFrame,  # mute=True
+            BotStoppedSpeakingFrame,
+            STTMuteFrame,  # mute=False
+        ]
+
+        await run_test(
+            filter,
+            frames_to_send=frames_to_send,
+            expected_down_frames=expected_returned_frames,
+        )
+
+    # TODO: Revisit once we figure out how to test SystemFrames and DataFrames
+    # async def test_function_call_strategy(self):
+    #     filter = STTMuteFilter(config=STTMuteConfig(strategies={STTMuteStrategy.FUNCTION_CALL}))
+
+    #     frames_to_send = [
+    #         UserStartedSpeakingFrame(),  # Should pass through initially
+    #         UserStoppedSpeakingFrame(),
+    #         FunctionCallInProgressFrame(
+    #             function_name="get_weather",
+    #             tool_call_id="call_123",
+    #             arguments='{"location": "San Francisco"}',
+    #         ),  # Start function call
+    #         UserStartedSpeakingFrame(),  # Should be suppressed
+    #         UserStoppedSpeakingFrame(),  # Should be suppressed
+    #         FunctionCallResultFrame(
+    #             function_name="get_weather",
+    #             tool_call_id="call_123",
+    #             arguments='{"location": "San Francisco"}',
+    #             result={"temperature": 22},
+    #         ),  # End function call
+    #         UserStartedSpeakingFrame(),  # Should pass through again
+    #         UserStoppedSpeakingFrame(),
+    #     ]
+
+    #     expected_returned_frames = [
+    #         UserStartedSpeakingFrame,
+    #         UserStoppedSpeakingFrame,
+    #         FunctionCallInProgressFrame,
+    #         STTMuteFrame,  # mute=True
+    #         FunctionCallResultFrame,
+    #         STTMuteFrame,  # mute=False
+    #         UserStartedSpeakingFrame,
+    #         UserStoppedSpeakingFrame,
+    #     ]
+
+    #     await run_test(
+    #         filter,
+    #         frames_to_send=frames_to_send,
+    #         expected_down_frames=expected_returned_frames,
+    #     )
+
+    async def test_mute_until_first_bot_complete_strategy(self):
+        filter = STTMuteFilter(
+            config=STTMuteConfig(strategies={STTMuteStrategy.MUTE_UNTIL_FIRST_BOT_COMPLETE})
+        )
+
+        frames_to_send = [
+            UserStartedSpeakingFrame(),  # Should be suppressed (starts muted)
+            UserStoppedSpeakingFrame(),  # Should be suppressed
+            BotStartedSpeakingFrame(),  # First bot speech
+            UserStartedSpeakingFrame(),  # Should be suppressed
+            UserStoppedSpeakingFrame(),  # Should be suppressed
+            BotStoppedSpeakingFrame(),  # First speech ends, unmutes
+            UserStartedSpeakingFrame(),  # Should pass through
+            UserStoppedSpeakingFrame(),  # Should pass through
+            BotStartedSpeakingFrame(),  # Second speech
+            UserStartedSpeakingFrame(),  # Should pass through
+            UserStoppedSpeakingFrame(),  # Should pass through
+            BotStoppedSpeakingFrame(),
+        ]
+
+        expected_returned_frames = [
+            STTMuteFrame,  # mute=True after first speech
+            BotStartedSpeakingFrame,
+            BotStoppedSpeakingFrame,
+            STTMuteFrame,  # mute=False after first speech
+            UserStartedSpeakingFrame,
+            UserStoppedSpeakingFrame,
+            BotStartedSpeakingFrame,
+            UserStartedSpeakingFrame,
+            UserStoppedSpeakingFrame,
+            BotStoppedSpeakingFrame,
+        ]
+
+        await run_test(
+            filter,
+            frames_to_send=frames_to_send,
+            expected_down_frames=expected_returned_frames,
+        )
+
+    async def test_incompatible_strategies(self):
+        with self.assertRaises(ValueError):
+            STTMuteFilter(
+                config=STTMuteConfig(
+                    strategies={
+                        STTMuteStrategy.FIRST_SPEECH,
+                        STTMuteStrategy.MUTE_UNTIL_FIRST_BOT_COMPLETE,
+                    }
+                )
+            )
+
+    async def test_custom_strategy(self):
+        async def custom_mute_logic(processor: STTMuteFilter) -> bool:
+            return processor._bot_is_speaking
+
+        filter = STTMuteFilter(
+            config=STTMuteConfig(
+                strategies={STTMuteStrategy.CUSTOM},
+                should_mute_callback=custom_mute_logic,
+            )
+        )
+
+        frames_to_send = [
+            UserStartedSpeakingFrame(),  # Should pass through
+            UserStoppedSpeakingFrame(),  # Should pass through
+            BotStartedSpeakingFrame(),  # Bot starts speaking
+            UserStartedSpeakingFrame(),  # Should be suppressed
+            UserStoppedSpeakingFrame(),  # Should be suppressed
+            BotStoppedSpeakingFrame(),  # Bot stops speaking
+            UserStartedSpeakingFrame(),  # Should pass through
+            UserStoppedSpeakingFrame(),  # Should pass through
+        ]
+
+        expected_returned_frames = [
+            UserStartedSpeakingFrame,
+            UserStoppedSpeakingFrame,
+            BotStartedSpeakingFrame,
+            STTMuteFrame,  # mute=True
+            BotStoppedSpeakingFrame,
+            STTMuteFrame,  # mute=False
+            UserStartedSpeakingFrame,
+            UserStoppedSpeakingFrame,
+        ]
+
+        await run_test(
+            filter,
+            frames_to_send=frames_to_send,
+            expected_down_frames=expected_returned_frames,
+        )