diff --git a/homeassistant/components/tuya/binary_sensor.py b/homeassistant/components/tuya/binary_sensor.py
index e28572228b1..fd3f0cfcb7e 100644
--- a/homeassistant/components/tuya/binary_sensor.py
+++ b/homeassistant/components/tuya/binary_sensor.py
@@ -320,6 +320,7 @@ BINARY_SENSORS: dict[str, tuple[TuyaBinarySensorEntityDescription, ...]] = {
         TuyaBinarySensorEntityDescription(
             key=DPCode.MASTER_STATE,
             device_class=BinarySensorDeviceClass.PROBLEM,
+            entity_category=EntityCategory.DIAGNOSTIC,
             on_value="alarm",
         ),
     ),
diff --git a/tests/components/tuya/snapshots/test_binary_sensor.ambr b/tests/components/tuya/snapshots/test_binary_sensor.ambr
index c9d2296e726..6ae0b4997dd 100644
--- a/tests/components/tuya/snapshots/test_binary_sensor.ambr
+++ b/tests/components/tuya/snapshots/test_binary_sensor.ambr
@@ -697,7 +697,7 @@
     'device_id': <ANY>,
     'disabled_by': None,
     'domain': 'binary_sensor',
-    'entity_category': None,
+    'entity_category': <EntityCategory.DIAGNOSTIC: 'diagnostic'>,
     'entity_id': 'binary_sensor.x5_zigbee_gateway_problem',
     'has_entity_name': True,
     'hidden_by': None,