diff --git a/homeassistant/components/knx/number.py b/homeassistant/components/knx/number.py
index d1ef2d226b4..c48c11fa998 100644
--- a/homeassistant/components/knx/number.py
+++ b/homeassistant/components/knx/number.py
@@ -75,6 +75,7 @@ class KNXNumber(KnxEntity, NumberEntity, RestoreEntity):
             self._device.sensor_value.dpt_class.resolution,
         )
         self._attr_unique_id = str(self._device.sensor_value.group_address)
+        self._attr_unit_of_measurement = self._device.unit_of_measurement()
         self._device.sensor_value.value = max(0, self._attr_min_value)
 
     async def async_added_to_hass(self) -> None:
diff --git a/tests/components/knx/test_number.py b/tests/components/knx/test_number.py
new file mode 100644
index 00000000000..1a2044b166c
--- /dev/null
+++ b/tests/components/knx/test_number.py
@@ -0,0 +1,23 @@
+"""Test KNX number."""
+from homeassistant.components.knx.const import KNX_ADDRESS
+from homeassistant.components.knx.schema import NumberSchema
+from homeassistant.const import CONF_NAME, CONF_TYPE
+from homeassistant.core import HomeAssistant
+
+from .conftest import KNXTestKit
+
+
+async def test_number_unit_of_measurement(hass: HomeAssistant, knx: KNXTestKit):
+    """Test simple KNX number."""
+    test_address = "1/1/1"
+    await knx.setup_integration(
+        {
+            NumberSchema.PLATFORM_NAME: {
+                CONF_NAME: "test",
+                KNX_ADDRESS: test_address,
+                CONF_TYPE: "illuminance",
+            }
+        }
+    )
+    assert len(hass.states.async_all()) == 1
+    assert hass.states.get("number.test").attributes.get("unit_of_measurement") == "lx"