diff --git a/homeassistant/components/vicare/diagnostics.py b/homeassistant/components/vicare/diagnostics.py
index 7695c304451e..b3a64fdad546 100644
--- a/homeassistant/components/vicare/diagnostics.py
+++ b/homeassistant/components/vicare/diagnostics.py
@@ -23,7 +23,7 @@ async def async_get_config_entry_diagnostics(
         """Dump devices."""
         return [
             json.loads(device.dump_secure())
-            for device in entry.runtime_data.client.devices
+            for device in entry.runtime_data.client.all_devices
         ]
 
     return {
diff --git a/tests/components/vicare/conftest.py b/tests/components/vicare/conftest.py
index c8feec8dc749..6709df2dbe95 100644
--- a/tests/components/vicare/conftest.py
+++ b/tests/components/vicare/conftest.py
@@ -45,6 +45,23 @@ class MockPyViCare:
                     "Online",
                 )
             )
+        # Simulate a device with an unsupported deviceType that PyViCare's
+        # `devices` filter would drop but should still appear in `all_devices`
+        # (used by diagnostics).
+        self.all_devices = [
+            *self.devices,
+            PyViCareDeviceConfig(
+                MockViCareService(
+                    "installation_unsupported",
+                    "gateway_unsupported",
+                    "device_unsupported",
+                    Fixture(set(), "vicare/dummy-device-no-serial.json"),
+                ),
+                "deviceId_unsupported",
+                "unsupported_model",
+                "Online",
+            ),
+        ]
 
 
 class MockViCareService:
diff --git a/tests/components/vicare/snapshots/test_diagnostics.ambr b/tests/components/vicare/snapshots/test_diagnostics.ambr
index e0ca73c7c5e4..3844a3f248cb 100644
--- a/tests/components/vicare/snapshots/test_diagnostics.ambr
+++ b/tests/components/vicare/snapshots/test_diagnostics.ambr
@@ -4720,6 +4720,18 @@
           'type': None,
         }),
       }),
+      dict({
+        'data': list([
+        ]),
+        'device': dict({
+          'id': 'deviceId_unsupported',
+          'modelId': 'unsupported_model',
+          'roles': list([
+          ]),
+          'status': 'Online',
+          'type': None,
+        }),
+      }),
     ]),
     'entry': dict({
       'data': dict({