diff --git a/homeassistant/components/brother/sensor.py b/homeassistant/components/brother/sensor.py
index 2768d0922fbf..21e46444c894 100644
--- a/homeassistant/components/brother/sensor.py
+++ b/homeassistant/components/brother/sensor.py
@@ -51,24 +51,28 @@ SENSOR_TYPES: tuple[BrotherSensorEntityDescription, ...] = (
         key="page_counter",
         translation_key="page_counter",
         state_class=SensorStateClass.MEASUREMENT,
+        entity_category=EntityCategory.DIAGNOSTIC,
         value=lambda data: data.page_counter,
     ),
     BrotherSensorEntityDescription(
         key="bw_counter",
         translation_key="bw_pages",
         state_class=SensorStateClass.MEASUREMENT,
+        entity_category=EntityCategory.DIAGNOSTIC,
         value=lambda data: data.bw_counter,
     ),
     BrotherSensorEntityDescription(
         key="color_counter",
         translation_key="color_pages",
         state_class=SensorStateClass.MEASUREMENT,
+        entity_category=EntityCategory.DIAGNOSTIC,
         value=lambda data: data.color_counter,
     ),
     BrotherSensorEntityDescription(
         key="duplex_unit_pages_counter",
         translation_key="duplex_unit_page_counter",
         state_class=SensorStateClass.MEASUREMENT,
+        entity_category=EntityCategory.DIAGNOSTIC,
         value=lambda data: data.duplex_unit_pages_counter,
     ),
     BrotherSensorEntityDescription(
@@ -76,18 +80,21 @@ SENSOR_TYPES: tuple[BrotherSensorEntityDescription, ...] = (
         translation_key="drum_remaining_life",
         native_unit_of_measurement=PERCENTAGE,
         state_class=SensorStateClass.MEASUREMENT,
+        entity_category=EntityCategory.DIAGNOSTIC,
         value=lambda data: data.drum_remaining_life,
     ),
     BrotherSensorEntityDescription(
         key="drum_remaining_pages",
         translation_key="drum_remaining_pages",
         state_class=SensorStateClass.MEASUREMENT,
+        entity_category=EntityCategory.DIAGNOSTIC,
         value=lambda data: data.drum_remaining_pages,
     ),
     BrotherSensorEntityDescription(
         key="drum_counter",
         translation_key="drum_page_counter",
         state_class=SensorStateClass.MEASUREMENT,
+        entity_category=EntityCategory.DIAGNOSTIC,
         value=lambda data: data.drum_counter,
     ),
     BrotherSensorEntityDescription(
@@ -95,18 +102,21 @@ SENSOR_TYPES: tuple[BrotherSensorEntityDescription, ...] = (
         translation_key="black_drum_remaining_life",
         native_unit_of_measurement=PERCENTAGE,
         state_class=SensorStateClass.MEASUREMENT,
+        entity_category=EntityCategory.DIAGNOSTIC,
         value=lambda data: data.black_drum_remaining_life,
     ),
     BrotherSensorEntityDescription(
         key="black_drum_remaining_pages",
         translation_key="black_drum_remaining_pages",
         state_class=SensorStateClass.MEASUREMENT,
+        entity_category=EntityCategory.DIAGNOSTIC,
         value=lambda data: data.black_drum_remaining_pages,
     ),
     BrotherSensorEntityDescription(
         key="black_drum_counter",
         translation_key="black_drum_page_counter",
         state_class=SensorStateClass.MEASUREMENT,
+        entity_category=EntityCategory.DIAGNOSTIC,
         value=lambda data: data.black_drum_counter,
     ),
     BrotherSensorEntityDescription(
@@ -114,18 +124,21 @@ SENSOR_TYPES: tuple[BrotherSensorEntityDescription, ...] = (
         translation_key="cyan_drum_remaining_life",
         native_unit_of_measurement=PERCENTAGE,
         state_class=SensorStateClass.MEASUREMENT,
+        entity_category=EntityCategory.DIAGNOSTIC,
         value=lambda data: data.cyan_drum_remaining_life,
     ),
     BrotherSensorEntityDescription(
         key="cyan_drum_remaining_pages",
         translation_key="cyan_drum_remaining_pages",
         state_class=SensorStateClass.MEASUREMENT,
+        entity_category=EntityCategory.DIAGNOSTIC,
         value=lambda data: data.cyan_drum_remaining_pages,
     ),
     BrotherSensorEntityDescription(
         key="cyan_drum_counter",
         translation_key="cyan_drum_page_counter",
         state_class=SensorStateClass.MEASUREMENT,
+        entity_category=EntityCategory.DIAGNOSTIC,
         value=lambda data: data.cyan_drum_counter,
     ),
     BrotherSensorEntityDescription(
@@ -133,18 +146,21 @@ SENSOR_TYPES: tuple[BrotherSensorEntityDescription, ...] = (
         translation_key="magenta_drum_remaining_life",
         native_unit_of_measurement=PERCENTAGE,
         state_class=SensorStateClass.MEASUREMENT,
+        entity_category=EntityCategory.DIAGNOSTIC,
         value=lambda data: data.magenta_drum_remaining_life,
     ),
     BrotherSensorEntityDescription(
         key="magenta_drum_remaining_pages",
         translation_key="magenta_drum_remaining_pages",
         state_class=SensorStateClass.MEASUREMENT,
+        entity_category=EntityCategory.DIAGNOSTIC,
         value=lambda data: data.magenta_drum_remaining_pages,
     ),
     BrotherSensorEntityDescription(
         key="magenta_drum_counter",
         translation_key="magenta_drum_page_counter",
         state_class=SensorStateClass.MEASUREMENT,
+        entity_category=EntityCategory.DIAGNOSTIC,
         value=lambda data: data.magenta_drum_counter,
     ),
     BrotherSensorEntityDescription(
@@ -152,18 +168,21 @@ SENSOR_TYPES: tuple[BrotherSensorEntityDescription, ...] = (
         translation_key="yellow_drum_remaining_life",
         native_unit_of_measurement=PERCENTAGE,
         state_class=SensorStateClass.MEASUREMENT,
+        entity_category=EntityCategory.DIAGNOSTIC,
         value=lambda data: data.yellow_drum_remaining_life,
     ),
     BrotherSensorEntityDescription(
         key="yellow_drum_remaining_pages",
         translation_key="yellow_drum_remaining_pages",
         state_class=SensorStateClass.MEASUREMENT,
+        entity_category=EntityCategory.DIAGNOSTIC,
         value=lambda data: data.yellow_drum_remaining_pages,
     ),
     BrotherSensorEntityDescription(
         key="yellow_drum_counter",
         translation_key="yellow_drum_page_counter",
         state_class=SensorStateClass.MEASUREMENT,
+        entity_category=EntityCategory.DIAGNOSTIC,
         value=lambda data: data.yellow_drum_counter,
     ),
     BrotherSensorEntityDescription(
@@ -171,6 +190,7 @@ SENSOR_TYPES: tuple[BrotherSensorEntityDescription, ...] = (
         translation_key="belt_unit_remaining_life",
         native_unit_of_measurement=PERCENTAGE,
         state_class=SensorStateClass.MEASUREMENT,
+        entity_category=EntityCategory.DIAGNOSTIC,
         value=lambda data: data.belt_unit_remaining_life,
     ),
     BrotherSensorEntityDescription(
@@ -178,6 +198,7 @@ SENSOR_TYPES: tuple[BrotherSensorEntityDescription, ...] = (
         translation_key="fuser_remaining_life",
         native_unit_of_measurement=PERCENTAGE,
         state_class=SensorStateClass.MEASUREMENT,
+        entity_category=EntityCategory.DIAGNOSTIC,
         value=lambda data: data.fuser_remaining_life,
     ),
     BrotherSensorEntityDescription(
@@ -185,6 +206,7 @@ SENSOR_TYPES: tuple[BrotherSensorEntityDescription, ...] = (
         translation_key="laser_remaining_life",
         native_unit_of_measurement=PERCENTAGE,
         state_class=SensorStateClass.MEASUREMENT,
+        entity_category=EntityCategory.DIAGNOSTIC,
         value=lambda data: data.laser_remaining_life,
     ),
     BrotherSensorEntityDescription(
@@ -192,6 +214,7 @@ SENSOR_TYPES: tuple[BrotherSensorEntityDescription, ...] = (
         translation_key="pf_kit_1_remaining_life",
         native_unit_of_measurement=PERCENTAGE,
         state_class=SensorStateClass.MEASUREMENT,
+        entity_category=EntityCategory.DIAGNOSTIC,
         value=lambda data: data.pf_kit_1_remaining_life,
     ),
     BrotherSensorEntityDescription(
@@ -199,6 +222,7 @@ SENSOR_TYPES: tuple[BrotherSensorEntityDescription, ...] = (
         translation_key="pf_kit_mp_remaining_life",
         native_unit_of_measurement=PERCENTAGE,
         state_class=SensorStateClass.MEASUREMENT,
+        entity_category=EntityCategory.DIAGNOSTIC,
         value=lambda data: data.pf_kit_mp_remaining_life,
     ),
     BrotherSensorEntityDescription(
diff --git a/tests/components/brother/snapshots/test_sensor.ambr b/tests/components/brother/snapshots/test_sensor.ambr
index 64b8a6cdcaec..877b22fccaa6 100644
--- a/tests/components/brother/snapshots/test_sensor.ambr
+++ b/tests/components/brother/snapshots/test_sensor.ambr
@@ -14,7 +14,7 @@
     'device_id': <ANY>,
     'disabled_by': None,
     'domain': 'sensor',
-    'entity_category': None,
+    'entity_category': <EntityCategory.DIAGNOSTIC: 'diagnostic'>,
     'entity_id': 'sensor.hl_l2340dw_b_w_pages',
     'has_entity_name': True,
     'hidden_by': None,
@@ -68,7 +68,7 @@
     'device_id': <ANY>,
     'disabled_by': None,
     'domain': 'sensor',
-    'entity_category': None,
+    'entity_category': <EntityCategory.DIAGNOSTIC: 'diagnostic'>,
     'entity_id': 'sensor.hl_l2340dw_belt_unit_remaining_lifetime',
     'has_entity_name': True,
     'hidden_by': None,
@@ -122,7 +122,7 @@
     'device_id': <ANY>,
     'disabled_by': None,
     'domain': 'sensor',
-    'entity_category': None,
+    'entity_category': <EntityCategory.DIAGNOSTIC: 'diagnostic'>,
     'entity_id': 'sensor.hl_l2340dw_black_drum_page_counter',
     'has_entity_name': True,
     'hidden_by': None,
@@ -176,7 +176,7 @@
     'device_id': <ANY>,
     'disabled_by': None,
     'domain': 'sensor',
-    'entity_category': None,
+    'entity_category': <EntityCategory.DIAGNOSTIC: 'diagnostic'>,
     'entity_id': 'sensor.hl_l2340dw_black_drum_remaining_lifetime',
     'has_entity_name': True,
     'hidden_by': None,
@@ -230,7 +230,7 @@
     'device_id': <ANY>,
     'disabled_by': None,
     'domain': 'sensor',
-    'entity_category': None,
+    'entity_category': <EntityCategory.DIAGNOSTIC: 'diagnostic'>,
     'entity_id': 'sensor.hl_l2340dw_black_drum_remaining_pages',
     'has_entity_name': True,
     'hidden_by': None,
@@ -338,7 +338,7 @@
     'device_id': <ANY>,
     'disabled_by': None,
     'domain': 'sensor',
-    'entity_category': None,
+    'entity_category': <EntityCategory.DIAGNOSTIC: 'diagnostic'>,
     'entity_id': 'sensor.hl_l2340dw_color_pages',
     'has_entity_name': True,
     'hidden_by': None,
@@ -392,7 +392,7 @@
     'device_id': <ANY>,
     'disabled_by': None,
     'domain': 'sensor',
-    'entity_category': None,
+    'entity_category': <EntityCategory.DIAGNOSTIC: 'diagnostic'>,
     'entity_id': 'sensor.hl_l2340dw_cyan_drum_page_counter',
     'has_entity_name': True,
     'hidden_by': None,
@@ -446,7 +446,7 @@
     'device_id': <ANY>,
     'disabled_by': None,
     'domain': 'sensor',
-    'entity_category': None,
+    'entity_category': <EntityCategory.DIAGNOSTIC: 'diagnostic'>,
     'entity_id': 'sensor.hl_l2340dw_cyan_drum_remaining_lifetime',
     'has_entity_name': True,
     'hidden_by': None,
@@ -500,7 +500,7 @@
     'device_id': <ANY>,
     'disabled_by': None,
     'domain': 'sensor',
-    'entity_category': None,
+    'entity_category': <EntityCategory.DIAGNOSTIC: 'diagnostic'>,
     'entity_id': 'sensor.hl_l2340dw_cyan_drum_remaining_pages',
     'has_entity_name': True,
     'hidden_by': None,
@@ -608,7 +608,7 @@
     'device_id': <ANY>,
     'disabled_by': None,
     'domain': 'sensor',
-    'entity_category': None,
+    'entity_category': <EntityCategory.DIAGNOSTIC: 'diagnostic'>,
     'entity_id': 'sensor.hl_l2340dw_drum_page_counter',
     'has_entity_name': True,
     'hidden_by': None,
@@ -662,7 +662,7 @@
     'device_id': <ANY>,
     'disabled_by': None,
     'domain': 'sensor',
-    'entity_category': None,
+    'entity_category': <EntityCategory.DIAGNOSTIC: 'diagnostic'>,
     'entity_id': 'sensor.hl_l2340dw_drum_remaining_lifetime',
     'has_entity_name': True,
     'hidden_by': None,
@@ -716,7 +716,7 @@
     'device_id': <ANY>,
     'disabled_by': None,
     'domain': 'sensor',
-    'entity_category': None,
+    'entity_category': <EntityCategory.DIAGNOSTIC: 'diagnostic'>,
     'entity_id': 'sensor.hl_l2340dw_drum_remaining_pages',
     'has_entity_name': True,
     'hidden_by': None,
@@ -770,7 +770,7 @@
     'device_id': <ANY>,
     'disabled_by': None,
     'domain': 'sensor',
-    'entity_category': None,
+    'entity_category': <EntityCategory.DIAGNOSTIC: 'diagnostic'>,
     'entity_id': 'sensor.hl_l2340dw_duplex_unit_page_counter',
     'has_entity_name': True,
     'hidden_by': None,
@@ -824,7 +824,7 @@
     'device_id': <ANY>,
     'disabled_by': None,
     'domain': 'sensor',
-    'entity_category': None,
+    'entity_category': <EntityCategory.DIAGNOSTIC: 'diagnostic'>,
     'entity_id': 'sensor.hl_l2340dw_fuser_remaining_lifetime',
     'has_entity_name': True,
     'hidden_by': None,
@@ -878,7 +878,7 @@
     'device_id': <ANY>,
     'disabled_by': None,
     'domain': 'sensor',
-    'entity_category': None,
+    'entity_category': <EntityCategory.DIAGNOSTIC: 'diagnostic'>,
     'entity_id': 'sensor.hl_l2340dw_magenta_drum_page_counter',
     'has_entity_name': True,
     'hidden_by': None,
@@ -932,7 +932,7 @@
     'device_id': <ANY>,
     'disabled_by': None,
     'domain': 'sensor',
-    'entity_category': None,
+    'entity_category': <EntityCategory.DIAGNOSTIC: 'diagnostic'>,
     'entity_id': 'sensor.hl_l2340dw_magenta_drum_remaining_lifetime',
     'has_entity_name': True,
     'hidden_by': None,
@@ -986,7 +986,7 @@
     'device_id': <ANY>,
     'disabled_by': None,
     'domain': 'sensor',
-    'entity_category': None,
+    'entity_category': <EntityCategory.DIAGNOSTIC: 'diagnostic'>,
     'entity_id': 'sensor.hl_l2340dw_magenta_drum_remaining_pages',
     'has_entity_name': True,
     'hidden_by': None,
@@ -1094,7 +1094,7 @@
     'device_id': <ANY>,
     'disabled_by': None,
     'domain': 'sensor',
-    'entity_category': None,
+    'entity_category': <EntityCategory.DIAGNOSTIC: 'diagnostic'>,
     'entity_id': 'sensor.hl_l2340dw_page_counter',
     'has_entity_name': True,
     'hidden_by': None,
@@ -1148,7 +1148,7 @@
     'device_id': <ANY>,
     'disabled_by': None,
     'domain': 'sensor',
-    'entity_category': None,
+    'entity_category': <EntityCategory.DIAGNOSTIC: 'diagnostic'>,
     'entity_id': 'sensor.hl_l2340dw_pf_kit_1_remaining_lifetime',
     'has_entity_name': True,
     'hidden_by': None,
@@ -1303,7 +1303,7 @@
     'device_id': <ANY>,
     'disabled_by': None,
     'domain': 'sensor',
-    'entity_category': None,
+    'entity_category': <EntityCategory.DIAGNOSTIC: 'diagnostic'>,
     'entity_id': 'sensor.hl_l2340dw_yellow_drum_page_counter',
     'has_entity_name': True,
     'hidden_by': None,
@@ -1357,7 +1357,7 @@
     'device_id': <ANY>,
     'disabled_by': None,
     'domain': 'sensor',
-    'entity_category': None,
+    'entity_category': <EntityCategory.DIAGNOSTIC: 'diagnostic'>,
     'entity_id': 'sensor.hl_l2340dw_yellow_drum_remaining_lifetime',
     'has_entity_name': True,
     'hidden_by': None,
@@ -1411,7 +1411,7 @@
     'device_id': <ANY>,
     'disabled_by': None,
     'domain': 'sensor',
-    'entity_category': None,
+    'entity_category': <EntityCategory.DIAGNOSTIC: 'diagnostic'>,
     'entity_id': 'sensor.hl_l2340dw_yellow_drum_remaining_pages',
     'has_entity_name': True,
     'hidden_by': None,