diff --git a/homeassistant/components/fan/__init__.py b/homeassistant/components/fan/__init__.py
index 2a96a16bf55..f2ade535426 100644
--- a/homeassistant/components/fan/__init__.py
+++ b/homeassistant/components/fan/__init__.py
@@ -73,7 +73,7 @@ FAN_TURN_ON_SCHEMA = vol.Schema({
 })  # type: dict
 
 FAN_TURN_OFF_SCHEMA = vol.Schema({
-    vol.Required(ATTR_ENTITY_ID): cv.entity_ids
+    vol.Optional(ATTR_ENTITY_ID): cv.entity_ids
 })  # type: dict
 
 FAN_OSCILLATE_SCHEMA = vol.Schema({
@@ -139,9 +139,7 @@ def turn_on(hass, entity_id: str=None, speed: str=None) -> None:
 
 def turn_off(hass, entity_id: str=None) -> None:
     """Turn all or specified fan off."""
-    data = {
-        ATTR_ENTITY_ID: entity_id,
-    }
+    data = {ATTR_ENTITY_ID: entity_id} if entity_id else {}
 
     hass.services.call(DOMAIN, SERVICE_TURN_OFF, data)
 
diff --git a/tests/components/fan/test_demo.py b/tests/components/fan/test_demo.py
index 517dcd494cc..0d066af8cf6 100644
--- a/tests/components/fan/test_demo.py
+++ b/tests/components/fan/test_demo.py
@@ -56,6 +56,18 @@ class TestDemoFan(unittest.TestCase):
         self.hass.block_till_done()
         self.assertEqual(STATE_OFF, self.get_entity().state)
 
+    def test_turn_off_without_entity_id(self):
+        """Test turning off all fans."""
+        self.assertEqual(STATE_OFF, self.get_entity().state)
+
+        fan.turn_on(self.hass, FAN_ENTITY_ID)
+        self.hass.block_till_done()
+        self.assertNotEqual(STATE_OFF, self.get_entity().state)
+
+        fan.turn_off(self.hass)
+        self.hass.block_till_done()
+        self.assertEqual(STATE_OFF, self.get_entity().state)
+
     def test_set_direction(self):
         """Test setting the direction of the device."""
         self.assertEqual(STATE_OFF, self.get_entity().state)