diff --git a/homeassistant/components/homekit/__init__.py b/homeassistant/components/homekit/__init__.py
index 8c12243ee8f..bd79a0a7ca7 100644
--- a/homeassistant/components/homekit/__init__.py
+++ b/homeassistant/components/homekit/__init__.py
@@ -28,10 +28,12 @@ from .const import (
 from .util import (
     show_setup_message, validate_entity_config, validate_media_player_features)
 
-TYPES = Registry()
+REQUIREMENTS = ['HAP-python==2.2.2']
+
 _LOGGER = logging.getLogger(__name__)
 
-REQUIREMENTS = ['HAP-python==2.2.2']
+MAX_DEVICES = 100
+TYPES = Registry()
 
 # #### Driver Status ####
 STATUS_READY = 0
@@ -239,6 +241,10 @@ class HomeKit():
         if not self.driver.state.paired:
             show_setup_message(self.hass, self.driver.state.pincode)
 
+        if len(self.bridge.accessories) > MAX_DEVICES:
+            _LOGGER.warning('You have exceeded the device limit, which might '
+                            'cause issues. Consider using the filter option.')
+
         _LOGGER.debug('Driver start')
         self.hass.add_job(self.driver.start)
         self.status = STATUS_RUNNING
diff --git a/tests/components/homekit/test_homekit.py b/tests/components/homekit/test_homekit.py
index f8afb4a49ab..a831a7e9e5d 100644
--- a/tests/components/homekit/test_homekit.py
+++ b/tests/components/homekit/test_homekit.py
@@ -5,8 +5,8 @@ import pytest
 
 from homeassistant import setup
 from homeassistant.components.homekit import (
-    generate_aid, HomeKit, STATUS_READY, STATUS_RUNNING,
-    STATUS_STOPPED, STATUS_WAIT)
+    generate_aid, HomeKit, MAX_DEVICES, STATUS_READY,
+    STATUS_RUNNING, STATUS_STOPPED, STATUS_WAIT)
 from homeassistant.components.homekit.accessories import HomeBridge
 from homeassistant.components.homekit.const import (
     CONF_AUTO_START, BRIDGE_NAME, DEFAULT_PORT, DOMAIN, HOMEKIT_FILE,
@@ -173,7 +173,8 @@ async def test_homekit_start(hass, hk_driver, debounce_patcher):
     """Test HomeKit start method."""
     pin = b'123-45-678'
     homekit = HomeKit(hass, None, None, None, {}, {'cover.demo': {}})
-    homekit.bridge = 'bridge'
+    homekit.bridge = Mock()
+    homekit.bridge.accessories = []
     homekit.driver = hk_driver
 
     hass.states.async_set('light.demo', 'on')
@@ -190,7 +191,7 @@ async def test_homekit_start(hass, hk_driver, debounce_patcher):
 
     mock_add_acc.assert_called_with(state)
     mock_setup_msg.assert_called_with(hass, pin)
-    hk_driver_add_acc.assert_called_with('bridge')
+    hk_driver_add_acc.assert_called_with(homekit.bridge)
     assert hk_driver_start.called
     assert homekit.status == STATUS_RUNNING
 
@@ -217,3 +218,18 @@ async def test_homekit_stop(hass):
     homekit.status = STATUS_RUNNING
     await hass.async_add_job(homekit.stop)
     assert homekit.driver.stop.called is True
+
+
+async def test_homekit_too_many_accessories(hass, hk_driver):
+    """Test adding too many accessories to HomeKit."""
+    homekit = HomeKit(hass, None, None, None, None, None)
+    homekit.bridge = Mock()
+    homekit.bridge.accessories = range(MAX_DEVICES + 1)
+    homekit.driver = hk_driver
+
+    with patch('pyhap.accessory_driver.AccessoryDriver.start'), \
+            patch('pyhap.accessory_driver.AccessoryDriver.add_accessory'), \
+            patch('homeassistant.components.homekit._LOGGER.warning') \
+            as mock_warn:
+        await hass.async_add_job(homekit.start)
+        assert mock_warn.called is True