diff --git a/homeassistant/components/aquacell/icons.json b/homeassistant/components/aquacell/icons.json
index d7383f54d72..255a964d218 100644
--- a/homeassistant/components/aquacell/icons.json
+++ b/homeassistant/components/aquacell/icons.json
@@ -1,6 +1,9 @@
 {
   "entity": {
     "sensor": {
+      "last_update": {
+        "default": "mdi:update"
+      },
       "salt_left_side_percentage": {
         "default": "mdi:basket-fill"
       },
diff --git a/homeassistant/components/aquacell/sensor.py b/homeassistant/components/aquacell/sensor.py
index 77cd3cdd60a..58d3548284e 100644
--- a/homeassistant/components/aquacell/sensor.py
+++ b/homeassistant/components/aquacell/sensor.py
@@ -4,6 +4,7 @@ from __future__ import annotations
 
 from collections.abc import Callable
 from dataclasses import dataclass
+from datetime import datetime
 
 from aioaquacell import Softener
 
@@ -28,7 +29,7 @@ PARALLEL_UPDATES = 1
 class SoftenerSensorEntityDescription(SensorEntityDescription):
     """Describes Softener sensor entity."""
 
-    value_fn: Callable[[Softener], StateType]
+    value_fn: Callable[[Softener], StateType | datetime]
 
 
 SENSORS: tuple[SoftenerSensorEntityDescription, ...] = (
@@ -77,6 +78,12 @@ SENSORS: tuple[SoftenerSensorEntityDescription, ...] = (
             "low",
         ],
     ),
+    SoftenerSensorEntityDescription(
+        key="last_update",
+        translation_key="last_update",
+        device_class=SensorDeviceClass.TIMESTAMP,
+        value_fn=lambda softener: softener.lastUpdate,
+    ),
 )
 
 
@@ -111,6 +118,6 @@ class SoftenerSensor(AquacellEntity, SensorEntity):
         self.entity_description = description
 
     @property
-    def native_value(self) -> StateType:
+    def native_value(self) -> StateType | datetime:
         """Return the state of the sensor."""
         return self.entity_description.value_fn(self.softener)
diff --git a/homeassistant/components/aquacell/strings.json b/homeassistant/components/aquacell/strings.json
index e07adf3c199..d2052fbd08e 100644
--- a/homeassistant/components/aquacell/strings.json
+++ b/homeassistant/components/aquacell/strings.json
@@ -21,6 +21,9 @@
   },
   "entity": {
     "sensor": {
+      "last_update": {
+        "name": "Last update"
+      },
       "salt_left_side_percentage": {
         "name": "Salt left side percentage"
       },
diff --git a/tests/components/aquacell/snapshots/test_sensor.ambr b/tests/components/aquacell/snapshots/test_sensor.ambr
index ec89cb34bca..f512b2a824d 100644
--- a/tests/components/aquacell/snapshots/test_sensor.ambr
+++ b/tests/components/aquacell/snapshots/test_sensor.ambr
@@ -49,6 +49,54 @@
     'state': '40',
   })
 # ---
+# name: test_sensors[sensor.aquacell_name_last_update-entry]
+  EntityRegistryEntrySnapshot({
+    'aliases': set({
+    }),
+    'area_id': None,
+    'capabilities': None,
+    'config_entry_id': <ANY>,
+    'config_subentry_id': <ANY>,
+    'device_class': None,
+    'device_id': <ANY>,
+    'disabled_by': None,
+    'domain': 'sensor',
+    'entity_category': None,
+    'entity_id': 'sensor.aquacell_name_last_update',
+    'has_entity_name': True,
+    'hidden_by': None,
+    'icon': None,
+    'id': <ANY>,
+    'labels': set({
+    }),
+    'name': None,
+    'options': dict({
+    }),
+    'original_device_class': <SensorDeviceClass.TIMESTAMP: 'timestamp'>,
+    'original_icon': None,
+    'original_name': 'Last update',
+    'platform': 'aquacell',
+    'previous_unique_id': None,
+    'supported_features': 0,
+    'translation_key': 'last_update',
+    'unique_id': 'DSN-last_update',
+    'unit_of_measurement': None,
+  })
+# ---
+# name: test_sensors[sensor.aquacell_name_last_update-state]
+  StateSnapshot({
+    'attributes': ReadOnlyDict({
+      'device_class': 'timestamp',
+      'friendly_name': 'AquaCell name Last update',
+    }),
+    'context': <ANY>,
+    'entity_id': 'sensor.aquacell_name_last_update',
+    'last_changed': <ANY>,
+    'last_reported': <ANY>,
+    'last_updated': <ANY>,
+    'state': '2024-05-10T07:44:30+00:00',
+  })
+# ---
 # name: test_sensors[sensor.aquacell_name_salt_left_side_percentage-entry]
   EntityRegistryEntrySnapshot({
     'aliases': set({