diff --git a/homeassistant/components/shelly/diagnostics.py b/homeassistant/components/shelly/diagnostics.py
index db69abc8f55..e70b76a7c00 100644
--- a/homeassistant/components/shelly/diagnostics.py
+++ b/homeassistant/components/shelly/diagnostics.py
@@ -24,6 +24,8 @@ async def async_get_config_entry_diagnostics(
     device_settings: str | dict = "not initialized"
     device_status: str | dict = "not initialized"
     bluetooth: str | dict = "not initialized"
+    last_error: str = "not initialized"
+
     if shelly_entry_data.block:
         block_coordinator = shelly_entry_data.block
         assert block_coordinator
@@ -55,6 +57,10 @@ async def async_get_config_entry_diagnostics(
                     "uptime",
                 ]
             }
+
+        if block_coordinator.device.last_error:
+            last_error = repr(block_coordinator.device.last_error)
+
     else:
         rpc_coordinator = shelly_entry_data.rpc
         assert rpc_coordinator
@@ -79,6 +85,9 @@ async def async_get_config_entry_diagnostics(
                 "scanner": await scanner.async_diagnostics(),
             }
 
+        if rpc_coordinator.device.last_error:
+            last_error = repr(rpc_coordinator.device.last_error)
+
     if isinstance(device_status, dict):
         device_status = async_redact_data(device_status, ["ssid"])
 
@@ -87,5 +96,6 @@ async def async_get_config_entry_diagnostics(
         "device_info": device_info,
         "device_settings": device_settings,
         "device_status": device_status,
+        "last_error": last_error,
         "bluetooth": bluetooth,
     }
diff --git a/tests/components/shelly/test_diagnostics.py b/tests/components/shelly/test_diagnostics.py
index f7f238f3327..4fc8ea6ca8f 100644
--- a/tests/components/shelly/test_diagnostics.py
+++ b/tests/components/shelly/test_diagnostics.py
@@ -1,9 +1,10 @@
 """Tests for Shelly diagnostics platform."""
 
-from unittest.mock import ANY, Mock
+from unittest.mock import ANY, Mock, PropertyMock
 
 from aioshelly.ble.const import BLE_SCAN_RESULT_EVENT
 from aioshelly.const import MODEL_25
+from aioshelly.exceptions import DeviceConnectionError
 import pytest
 
 from homeassistant.components.diagnostics import REDACTED
@@ -36,6 +37,10 @@ async def test_block_config_entry_diagnostics(
         {key: REDACTED for key in TO_REDACT if key in entry_dict["data"]}
     )
 
+    type(mock_block_device).last_error = PropertyMock(
+        return_value=DeviceConnectionError()
+    )
+
     result = await get_diagnostics_for_config_entry(hass, hass_client, entry)
 
     assert result == {
@@ -48,6 +53,7 @@ async def test_block_config_entry_diagnostics(
         },
         "device_settings": {"coiot": {"update_period": 15}},
         "device_status": MOCK_STATUS_COAP,
+        "last_error": "DeviceConnectionError()",
     }
 
 
@@ -91,6 +97,10 @@ async def test_rpc_config_entry_diagnostics(
         {key: REDACTED for key in TO_REDACT if key in entry_dict["data"]}
     )
 
+    type(mock_rpc_device).last_error = PropertyMock(
+        return_value=DeviceConnectionError()
+    )
+
     result = await get_diagnostics_for_config_entry(hass, hass_client, entry)
 
     assert result == {
@@ -152,4 +162,5 @@ async def test_rpc_config_entry_diagnostics(
             },
             "wifi": {"rssi": -63},
         },
+        "last_error": "DeviceConnectionError()",
     }