diff --git a/homeassistant/components/roomba/icons.json b/homeassistant/components/roomba/icons.json
index cdb36ef97e5..8466ecb51e3 100644
--- a/homeassistant/components/roomba/icons.json
+++ b/homeassistant/components/roomba/icons.json
@@ -32,6 +32,9 @@
       },
       "total_cleaned_area": {
         "default": "mdi:texture-box"
+      },
+      "last_mission": {
+        "default": "mdi:calendar-clock"
       }
     }
   }
diff --git a/homeassistant/components/roomba/irobot_base.py b/homeassistant/components/roomba/irobot_base.py
index 4850dc0b7e9..07d05a28b89 100644
--- a/homeassistant/components/roomba/irobot_base.py
+++ b/homeassistant/components/roomba/irobot_base.py
@@ -118,6 +118,15 @@ class IRobotEntity(Entity):
         """Return the battery stats."""
         return self.vacuum_state.get("bbchg3", {})
 
+    @property
+    def last_mission(self):
+        """Return last mission start time."""
+        if (
+            ts := self.vacuum_state.get("cleanMissionStatus", {}).get("mssnStrtTm")
+        ) is None or ts == 0:
+            return None
+        return dt_util.utc_from_timestamp(ts)
+
     @property
     def _robot_state(self):
         """Return the state of the vacuum cleaner."""
diff --git a/homeassistant/components/roomba/sensor.py b/homeassistant/components/roomba/sensor.py
index 6e043d237f3..e0aaf5d8c6e 100644
--- a/homeassistant/components/roomba/sensor.py
+++ b/homeassistant/components/roomba/sensor.py
@@ -116,6 +116,14 @@ SENSORS: list[RoombaSensorEntityDescription] = [
         suggested_display_precision=0,
         entity_registry_enabled_default=False,
     ),
+    RoombaSensorEntityDescription(
+        key="last_mission",
+        translation_key="last_mission",
+        device_class=SensorDeviceClass.TIMESTAMP,
+        entity_category=EntityCategory.DIAGNOSTIC,
+        value_fn=lambda self: self.last_mission,
+        entity_registry_enabled_default=False,
+    ),
 ]
 
 
diff --git a/homeassistant/components/roomba/strings.json b/homeassistant/components/roomba/strings.json
index 088918824d2..0db70a6a141 100644
--- a/homeassistant/components/roomba/strings.json
+++ b/homeassistant/components/roomba/strings.json
@@ -87,6 +87,9 @@
       },
       "total_cleaned_area": {
         "name": "Total cleaned area"
+      },
+      "last_mission": {
+        "name": "Last mission start time"
       }
     }
   }