diff --git a/homeassistant/components/google_assistant/trait.py b/homeassistant/components/google_assistant/trait.py
index 5ae72b7a41ae7..cf9f360d4693b 100644
--- a/homeassistant/components/google_assistant/trait.py
+++ b/homeassistant/components/google_assistant/trait.py
@@ -1201,6 +1201,17 @@ class TemperatureSettingTrait(_Trait):
     preset_to_google = {climate.PRESET_ECO: "eco"}
     google_to_preset = {value: key for key, value in preset_to_google.items()}
 
+    action_to_google = {
+        climate.HVACAction.OFF: "off",
+        climate.HVACAction.HEATING: "heat",
+        climate.HVACAction.DEFROSTING: "heat",
+        climate.HVACAction.PREHEATING: "heat",
+        climate.HVACAction.COOLING: "cool",
+        climate.HVACAction.DRYING: "dry",
+        climate.HVACAction.FAN: "fan-only",
+        climate.HVACAction.IDLE: "none",
+    }
+
     @staticmethod
     def supported(domain, features, device_class, _):
         """Test if state is supported."""
@@ -1282,6 +1293,11 @@ def query_attributes(self) -> dict[str, Any]:
         else:
             response["thermostatMode"] = self.hvac_to_google.get(operation, "none")
 
+        if (
+            action := self.action_to_google.get(attrs.get(climate.ATTR_HVAC_ACTION))
+        ) is not None:
+            response["activeThermostatMode"] = action
+
         current_temp = attrs.get(climate.ATTR_CURRENT_TEMPERATURE)
         if current_temp is not None:
             response["thermostatTemperatureAmbient"] = round(
diff --git a/tests/components/google_assistant/test_google_assistant.py b/tests/components/google_assistant/test_google_assistant.py
index 3a7efe2b9b60c..001f637ba3065 100644
--- a/tests/components/google_assistant/test_google_assistant.py
+++ b/tests/components/google_assistant/test_google_assistant.py
@@ -231,6 +231,7 @@ async def test_query_climate_request(
     devices = body["payload"]["devices"]
     assert len(devices) == 3
     assert devices["climate.heatpump"] == {
+        "activeThermostatMode": "heat",
         "online": True,
         "on": True,
         "thermostatTemperatureSetpoint": 20.0,
@@ -247,6 +248,7 @@ async def test_query_climate_request(
         "currentFanSpeedSetting": "auto_low",
     }
     assert devices["climate.hvac"] == {
+        "activeThermostatMode": "cool",
         "online": True,
         "on": True,
         "thermostatTemperatureSetpoint": 21,
@@ -295,6 +297,7 @@ async def test_query_climate_request_f(
     devices = body["payload"]["devices"]
     assert len(devices) == 3
     assert devices["climate.heatpump"] == {
+        "activeThermostatMode": "heat",
         "online": True,
         "on": True,
         "thermostatTemperatureSetpoint": -6.7,
@@ -311,6 +314,7 @@ async def test_query_climate_request_f(
         "currentFanSpeedSetting": "auto_low",
     }
     assert devices["climate.hvac"] == {
+        "activeThermostatMode": "cool",
         "online": True,
         "on": True,
         "thermostatTemperatureSetpoint": -6.1,
diff --git a/tests/components/google_assistant/test_trait.py b/tests/components/google_assistant/test_trait.py
index ee2ab12788946..c9f5646e9f064 100644
--- a/tests/components/google_assistant/test_trait.py
+++ b/tests/components/google_assistant/test_trait.py
@@ -1625,6 +1625,44 @@ async def test_temperature_setting_climate_setpoint_auto(hass: HomeAssistant) ->
     assert calls[0].data == {ATTR_ENTITY_ID: "climate.bla", ATTR_TEMPERATURE: 19}
 
 
+async def test_temperature_setting_action_change(hass: HomeAssistant) -> None:
+    """Test that activeThermostatMode contains the current HVAC action."""
+    trt_idle = trait.TemperatureSettingTrait(
+        hass,
+        State(
+            "climate.bla",
+            climate.HVACMode.COOL,
+            {
+                climate.ATTR_HVAC_MODES: [climate.HVACMode.OFF, climate.HVACMode.COOL],
+                climate.ATTR_HVAC_ACTION: climate.HVACAction.IDLE,
+                climate.ATTR_CURRENT_TEMPERATURE: 18,
+                climate.ATTR_MIN_TEMP: 10,
+                climate.ATTR_MAX_TEMP: 30,
+                ATTR_TEMPERATURE: 18,
+            },
+        ),
+        BASIC_CONFIG,
+    )
+    assert trt_idle.query_attributes().get("activeThermostatMode") == "none"
+    trt_cool = trait.TemperatureSettingTrait(
+        hass,
+        State(
+            "climate.bla",
+            climate.HVACMode.COOL,
+            {
+                climate.ATTR_HVAC_MODES: [climate.HVACMode.OFF, climate.HVACMode.COOL],
+                climate.ATTR_HVAC_ACTION: climate.HVACAction.COOLING,
+                climate.ATTR_CURRENT_TEMPERATURE: 23,
+                climate.ATTR_MIN_TEMP: 10,
+                climate.ATTR_MAX_TEMP: 30,
+                ATTR_TEMPERATURE: 18,
+            },
+        ),
+        BASIC_CONFIG,
+    )
+    assert trt_cool.query_attributes().get("activeThermostatMode") == "cool"
+
+
 async def test_temperature_control(hass: HomeAssistant) -> None:
     """Test TemperatureControl trait support for sensor domain."""
     trt = trait.TemperatureControlTrait(