diff --git a/homeassistant/components/esphome/sensor.py b/homeassistant/components/esphome/sensor.py
index ceb391f6bda..12319be8c40 100644
--- a/homeassistant/components/esphome/sensor.py
+++ b/homeassistant/components/esphome/sensor.py
@@ -6,10 +6,15 @@ import math
 from aioesphomeapi import SensorInfo, SensorState, TextSensorInfo, TextSensorState
 import voluptuous as vol
 
-from homeassistant.components.sensor import DEVICE_CLASSES, SensorEntity
+from homeassistant.components.sensor import (
+    DEVICE_CLASS_TIMESTAMP,
+    DEVICE_CLASSES,
+    SensorEntity,
+)
 from homeassistant.config_entries import ConfigEntry
 from homeassistant.core import HomeAssistant
 import homeassistant.helpers.config_validation as cv
+from homeassistant.util import dt
 
 from . import EsphomeEntity, esphome_state_property, platform_async_setup_entry
 
@@ -74,6 +79,8 @@ class EsphomeSensor(EsphomeEntity, SensorEntity):
             return None
         if self._state.missing_state:
             return None
+        if self.device_class == DEVICE_CLASS_TIMESTAMP:
+            return dt.utc_from_timestamp(self._state.state).isoformat()
         return f"{self._state.state:.{self._static_info.accuracy_decimals}f}"
 
     @property