diff --git a/homeassistant/components/uptime/sensor.py b/homeassistant/components/uptime/sensor.py
index 1ccc0062461..12c00c7f96d 100644
--- a/homeassistant/components/uptime/sensor.py
+++ b/homeassistant/components/uptime/sensor.py
@@ -19,7 +19,7 @@ PLATFORM_SCHEMA = PLATFORM_SCHEMA.extend(
     {
         vol.Optional(CONF_NAME, default=DEFAULT_NAME): cv.string,
         vol.Optional(CONF_UNIT_OF_MEASUREMENT, default="days"): vol.All(
-            cv.string, vol.In(["minutes", "hours", "days"])
+            cv.string, vol.In(["minutes", "hours", "days", "seconds"])
         ),
     }
 )
@@ -72,6 +72,8 @@ class UptimeSensor(Entity):
             div_factor *= 24
         elif self.unit_of_measurement == "minutes":
             div_factor /= 60
+        elif self.unit_of_measurement == "seconds":
+            div_factor /= 3600
 
         delta = delta.total_seconds() / div_factor
         self._state = round(delta, 2)