diff --git a/homeassistant/components/prometheus/__init__.py b/homeassistant/components/prometheus/__init__.py
index 845178cdbd2..5987b6f27be 100644
--- a/homeassistant/components/prometheus/__init__.py
+++ b/homeassistant/components/prometheus/__init__.py
@@ -13,6 +13,11 @@ from homeassistant.components.climate.const import (
     CURRENT_HVAC_ACTIONS,
 )
 from homeassistant.components.http import HomeAssistantView
+from homeassistant.components.humidifier.const import (
+    ATTR_AVAILABLE_MODES,
+    ATTR_HUMIDITY,
+    ATTR_MODE,
+)
 from homeassistant.const import (
     ATTR_DEVICE_CLASS,
     ATTR_TEMPERATURE,
@@ -318,6 +323,32 @@ class PrometheusMetrics:
                     float(action == current_action)
                 )
 
+    def _handle_humidifier(self, state):
+        humidity = state.attributes.get(ATTR_HUMIDITY)
+        if humidity:
+            metric = self._metric(
+                "humidity", self.prometheus_cli.Gauge, "Target Relative Humidity"
+            )
+            metric.labels(**self._labels(state)).set(humidity)
+
+        metric = self._metric(
+            "humidifier_state",
+            self.prometheus_cli.Gauge,
+            "State of the humidifier (0/1)",
+        )
+        try:
+            value = self.state_as_number(state)
+        except ValueError:
+            value = 0.0
+        metric.labels(**self._labels(state)).set(value)
+
+        mode = state.attributes.get(ATTR_MODE)
+        modes = state.attributes.get(ATTR_AVAILABLE_MODES)
+        if mode and modes:
+            metric = self._metric("mode", self.prometheus_cli.Gauge, "Humidifier Mode")
+            value = modes.index(mode)
+            metric.labels(**self._labels(state)).set(value)
+
     def _handle_sensor(self, state):
         unit = self._unit_string(state.attributes.get(ATTR_UNIT_OF_MEASUREMENT))
 
diff --git a/tests/components/prometheus/test_init.py b/tests/components/prometheus/test_init.py
index 4539948cc5a..ce612d78ef7 100644
--- a/tests/components/prometheus/test_init.py
+++ b/tests/components/prometheus/test_init.py
@@ -2,7 +2,7 @@
 import pytest
 
 from homeassistant import setup
-from homeassistant.components import climate, sensor
+from homeassistant.components import climate, humidifier, sensor
 from homeassistant.components.demo.sensor import DemoSensor
 import homeassistant.components.prometheus as prometheus
 from homeassistant.const import (
@@ -28,6 +28,10 @@ async def prometheus_client(loop, hass, hass_client):
     )
     await hass.async_block_till_done()
 
+    await setup.async_setup_component(
+        hass, humidifier.DOMAIN, {"humidifier": [{"platform": "demo"}]}
+    )
+
     sensor1 = DemoSensor(
         None, "Television Energy", 74, None, ENERGY_KILO_WATT_HOUR, None
     )
@@ -104,6 +108,24 @@ async def test_view(prometheus_client):  # pylint: disable=redefined-outer-name
         'friendly_name="HeatPump"} 25.0' in body
     )
 
+    assert (
+        'humidity{domain="humidifier",'
+        'entity="humidifier.humidifier",'
+        'friendly_name="Humidifier"} 68.0' in body
+    )
+
+    assert (
+        'humidifier_state{domain="humidifier",'
+        'entity="humidifier.dehumidifier",'
+        'friendly_name="Dehumidifier"} 1.0' in body
+    )
+
+    assert (
+        'mode{domain="humidifier",'
+        'entity="humidifier.hygrostat",'
+        'friendly_name="Hygrostat"} 0.0' in body
+    )
+
     assert (
         'humidity_percent{domain="sensor",'
         'entity="sensor.outside_humidity",'