diff --git a/homeassistant/components/homekit_controller/binary_sensor.py b/homeassistant/components/homekit_controller/binary_sensor.py
index 939c6055e10..29fddf99189 100644
--- a/homeassistant/components/homekit_controller/binary_sensor.py
+++ b/homeassistant/components/homekit_controller/binary_sensor.py
@@ -4,6 +4,7 @@ import logging
 from aiohomekit.model.characteristics import CharacteristicsTypes
 
 from homeassistant.components.binary_sensor import (
+    DEVICE_CLASS_GAS,
     DEVICE_CLASS_MOISTURE,
     DEVICE_CLASS_MOTION,
     DEVICE_CLASS_OCCUPANCY,
@@ -72,6 +73,24 @@ class HomeKitSmokeSensor(HomeKitEntity, BinarySensorEntity):
         return self.service.value(CharacteristicsTypes.SMOKE_DETECTED) == 1
 
 
+class HomeKitCarbonMonoxideSensor(HomeKitEntity, BinarySensorEntity):
+    """Representation of a Homekit BO sensor."""
+
+    @property
+    def device_class(self) -> str:
+        """Return the class of this sensor."""
+        return DEVICE_CLASS_GAS
+
+    def get_characteristic_types(self):
+        """Define the homekit characteristics the entity is tracking."""
+        return [CharacteristicsTypes.CARBON_MONOXIDE_DETECTED]
+
+    @property
+    def is_on(self):
+        """Return true if CO is currently detected."""
+        return self.service.value(CharacteristicsTypes.CARBON_MONOXIDE_DETECTED) == 1
+
+
 class HomeKitOccupancySensor(HomeKitEntity, BinarySensorEntity):
     """Representation of a Homekit occupancy sensor."""
 
@@ -112,6 +131,7 @@ ENTITY_TYPES = {
     "motion": HomeKitMotionSensor,
     "contact": HomeKitContactSensor,
     "smoke": HomeKitSmokeSensor,
+    "carbon-monoxide": HomeKitCarbonMonoxideSensor,
     "occupancy": HomeKitOccupancySensor,
     "leak": HomeKitLeakSensor,
 }
diff --git a/homeassistant/components/homekit_controller/const.py b/homeassistant/components/homekit_controller/const.py
index 394750c0688..2a8a106a296 100644
--- a/homeassistant/components/homekit_controller/const.py
+++ b/homeassistant/components/homekit_controller/const.py
@@ -28,6 +28,7 @@ HOMEKIT_ACCESSORY_DISPATCH = {
     "temperature": "sensor",
     "battery": "sensor",
     "smoke": "binary_sensor",
+    "carbon-monoxide": "binary_sensor",
     "leak": "binary_sensor",
     "fan": "fan",
     "fanv2": "fan",
diff --git a/tests/components/homekit_controller/test_binary_sensor.py b/tests/components/homekit_controller/test_binary_sensor.py
index 460d14d0d48..e9ba4420176 100644
--- a/tests/components/homekit_controller/test_binary_sensor.py
+++ b/tests/components/homekit_controller/test_binary_sensor.py
@@ -3,6 +3,7 @@ from aiohomekit.model.characteristics import CharacteristicsTypes
 from aiohomekit.model.services import ServicesTypes
 
 from homeassistant.components.binary_sensor import (
+    DEVICE_CLASS_GAS,
     DEVICE_CLASS_MOISTURE,
     DEVICE_CLASS_MOTION,
     DEVICE_CLASS_OCCUPANCY,
@@ -15,6 +16,7 @@ from tests.components.homekit_controller.common import setup_test_component
 MOTION_DETECTED = ("motion", "motion-detected")
 CONTACT_STATE = ("contact", "contact-state")
 SMOKE_DETECTED = ("smoke", "smoke-detected")
+CARBON_MONOXIDE_DETECTED = ("carbon-monoxide", "carbon-monoxide.detected")
 OCCUPANCY_DETECTED = ("occupancy", "occupancy-detected")
 LEAK_DETECTED = ("leak", "leak-detected")
 
@@ -88,6 +90,29 @@ async def test_smoke_sensor_read_state(hass, utcnow):
     assert state.attributes["device_class"] == DEVICE_CLASS_SMOKE
 
 
+def create_carbon_monoxide_sensor_service(accessory):
+    """Define carbon monoxide sensor characteristics."""
+    service = accessory.add_service(ServicesTypes.CARBON_MONOXIDE_SENSOR)
+
+    cur_state = service.add_char(CharacteristicsTypes.CARBON_MONOXIDE_DETECTED)
+    cur_state.value = 0
+
+
+async def test_carbon_monoxide_sensor_read_state(hass, utcnow):
+    """Test that we can read the state of a HomeKit contact accessory."""
+    helper = await setup_test_component(hass, create_carbon_monoxide_sensor_service)
+
+    helper.characteristics[CARBON_MONOXIDE_DETECTED].value = 0
+    state = await helper.poll_and_get_state()
+    assert state.state == "off"
+
+    helper.characteristics[CARBON_MONOXIDE_DETECTED].value = 1
+    state = await helper.poll_and_get_state()
+    assert state.state == "on"
+
+    assert state.attributes["device_class"] == DEVICE_CLASS_GAS
+
+
 def create_occupancy_sensor_service(accessory):
     """Define occupancy characteristics."""
     service = accessory.add_service(ServicesTypes.OCCUPANCY_SENSOR)