diff --git a/homeassistant/components/growatt_server/coordinator.py b/homeassistant/components/growatt_server/coordinator.py
index f5da2779580b3..c9885f16dad56 100644
--- a/homeassistant/components/growatt_server/coordinator.py
+++ b/homeassistant/components/growatt_server/coordinator.py
@@ -215,14 +215,15 @@ def _sync_update_data(self) -> dict[str, Any]:
             mix_chart_entries = mix_detail["chartData"]
             sorted_keys = sorted(mix_chart_entries)
 
-            # Create datetime from the latest entry
-            date_now = dt_util.now().date()
-            last_updated_time = dt_util.parse_time(str(sorted_keys[-1]))
-            mix_detail["lastdataupdate"] = datetime.datetime.combine(
-                date_now,
-                last_updated_time,  # type: ignore[arg-type]
-                dt_util.get_default_time_zone(),
-            )
+            if sorted_keys:
+                # Create datetime from the latest entry
+                date_now = dt_util.now().date()
+                last_updated_time = dt_util.parse_time(str(sorted_keys[-1]))
+                mix_detail["lastdataupdate"] = datetime.datetime.combine(
+                    date_now,
+                    last_updated_time,  # type: ignore[arg-type]
+                    dt_util.get_default_time_zone(),
+                )
 
             # Dashboard data for mix system
             dashboard_data = self.api.dashboard_data(self.plant_id)
diff --git a/tests/components/growatt_server/test_sensor.py b/tests/components/growatt_server/test_sensor.py
index e64a2a864e2c8..81e31ba5ba989 100644
--- a/tests/components/growatt_server/test_sensor.py
+++ b/tests/components/growatt_server/test_sensor.py
@@ -127,6 +127,29 @@ async def test_sensors_classic_api(
     )
 
 
+@pytest.mark.freeze_time("2023-10-21")
+async def test_mix_empty_chart_data(
+    hass: HomeAssistant,
+    mock_growatt_classic_api,
+    mock_config_entry_classic: MockConfigEntry,
+) -> None:
+    """Test mix device handles empty chart data without crashing."""
+    mock_growatt_classic_api.device_list.return_value = [
+        {"deviceSn": "MIX123456", "deviceType": "mix"}
+    ]
+    mock_growatt_classic_api.mix_detail.return_value = {
+        "deviceSn": "MIX123456",
+        "chartData": {},
+    }
+
+    with patch("homeassistant.components.growatt_server.PLATFORMS", [Platform.SENSOR]):
+        await setup_integration(hass, mock_config_entry_classic)
+
+    # Should not crash - entities should still be created
+    states = hass.states.async_entity_ids("sensor")
+    assert len(states) > 0
+
+
 async def test_sensor_coordinator_updates(
     hass: HomeAssistant,
     mock_growatt_v1_api,