diff --git a/homeassistant/components/person/__init__.py b/homeassistant/components/person/__init__.py
index df19d86bb5c..20014c3414b 100644
--- a/homeassistant/components/person/__init__.py
+++ b/homeassistant/components/person/__init__.py
@@ -15,7 +15,7 @@ from homeassistant.components.device_tracker import (
     DOMAIN as DEVICE_TRACKER_DOMAIN)
 from homeassistant.const import (
     ATTR_ID, ATTR_LATITUDE, ATTR_LONGITUDE, CONF_ID, CONF_NAME,
-    EVENT_HOMEASSISTANT_START)
+    EVENT_HOMEASSISTANT_START, STATE_UNKNOWN, STATE_UNAVAILABLE)
 from homeassistant.core import callback, Event
 from homeassistant.auth import EVENT_USER_REMOVED
 import homeassistant.helpers.config_validation as cv
@@ -25,7 +25,6 @@ from homeassistant.helpers.event import async_track_state_change
 from homeassistant.helpers.restore_state import RestoreEntity
 from homeassistant.components import websocket_api
 from homeassistant.helpers.typing import HomeAssistantType, ConfigType
-from homeassistant.util import dt as dt_util
 from homeassistant.loader import bind_hass
 
 _LOGGER = logging.getLogger(__name__)
@@ -38,6 +37,8 @@ DOMAIN = 'person'
 STORAGE_KEY = DOMAIN
 STORAGE_VERSION = 1
 SAVE_DELAY = 10
+# Device tracker states to ignore
+IGNORE_STATES = (STATE_UNKNOWN, STATE_UNAVAILABLE)
 
 PERSON_SCHEMA = vol.Schema({
     vol.Required(CONF_ID): cv.string,
@@ -350,30 +351,31 @@ class Person(RestoreEntity):
         trackers = self._config.get(CONF_DEVICE_TRACKERS)
 
         if trackers:
-            def sort_key(state):
-                if state:
-                    return state.last_updated
-                return dt_util.utc_from_timestamp(0)
-
-            latest = max(
-                [self.hass.states.get(entity_id) for entity_id in trackers],
-                key=sort_key
-            )
-
-            @callback
-            def async_handle_tracker_update(entity, old_state, new_state):
-                """Handle the device tracker state changes."""
-                self._parse_source_state(new_state)
-                self.async_schedule_update_ha_state()
-
             _LOGGER.debug(
                 "Subscribe to device trackers for %s", self.entity_id)
 
             self._unsub_track_device = async_track_state_change(
-                self.hass, trackers, async_handle_tracker_update)
+                self.hass, trackers, self._async_handle_tracker_update)
 
-        else:
-            latest = None
+        self._update_state()
+
+    @callback
+    def _async_handle_tracker_update(self, entity, old_state, new_state):
+        """Handle the device tracker state changes."""
+        self._update_state()
+
+    @callback
+    def _update_state(self):
+        """Update the state."""
+        latest = None
+        for entity_id in self._config.get(CONF_DEVICE_TRACKERS, []):
+            state = self.hass.states.get(entity_id)
+
+            if not state or state.state in IGNORE_STATES:
+                continue
+
+            if latest is None or state.last_updated > latest.last_updated:
+                latest = state
 
         if latest:
             self._parse_source_state(latest)
diff --git a/tests/components/person/test_init.py b/tests/components/person/test_init.py
index 4cef84746ed..2eacb162f8e 100644
--- a/tests/components/person/test_init.py
+++ b/tests/components/person/test_init.py
@@ -29,7 +29,7 @@ def storage_setup(hass, hass_storage, hass_admin_user):
                     'id': '1234',
                     'name': 'tracked person',
                     'user_id': hass_admin_user.id,
-                    'device_trackers': DEVICE_TRACKER
+                    'device_trackers': [DEVICE_TRACKER]
                 }
             ]
         }
@@ -189,6 +189,43 @@ async def test_setup_two_trackers(hass, hass_admin_user):
     assert state.attributes.get(ATTR_USER_ID) == user_id
 
 
+async def test_ignore_unavailable_states(hass, hass_admin_user):
+    """Test set up person with two device trackers, one unavailable."""
+    user_id = hass_admin_user.id
+    config = {DOMAIN: {
+        'id': '1234', 'name': 'tracked person', 'user_id': user_id,
+        'device_trackers': [DEVICE_TRACKER, DEVICE_TRACKER_2]}}
+    assert await async_setup_component(hass, DOMAIN, config)
+
+    state = hass.states.get('person.tracked_person')
+    assert state.state == STATE_UNKNOWN
+
+    hass.bus.async_fire(EVENT_HOMEASSISTANT_START)
+    await hass.async_block_till_done()
+    hass.states.async_set(DEVICE_TRACKER, 'home')
+    await hass.async_block_till_done()
+    hass.states.async_set(DEVICE_TRACKER, 'unavailable')
+    await hass.async_block_till_done()
+
+    # Unknown, as only 1 device tracker has a state, but we ignore that one
+    state = hass.states.get('person.tracked_person')
+    assert state.state == STATE_UNKNOWN
+
+    hass.states.async_set(DEVICE_TRACKER_2, 'not_home')
+    await hass.async_block_till_done()
+
+    # Take state of tracker 2
+    state = hass.states.get('person.tracked_person')
+    assert state.state == 'not_home'
+
+    # state 1 is newer but ignored, keep tracker 2 state
+    hass.states.async_set(DEVICE_TRACKER, 'unknown')
+    await hass.async_block_till_done()
+
+    state = hass.states.get('person.tracked_person')
+    assert state.state == 'not_home'
+
+
 async def test_restore_home_state(hass, hass_admin_user):
     """Test that the state is restored for a person on startup."""
     user_id = hass_admin_user.id