diff --git a/homeassistant/components/bsblan/diagnostics.py b/homeassistant/components/bsblan/diagnostics.py
new file mode 100644
index 00000000000..91d959ea0e2
--- /dev/null
+++ b/homeassistant/components/bsblan/diagnostics.py
@@ -0,0 +1,22 @@
+"""Diagnostics support for BSBLan."""
+from __future__ import annotations
+
+from typing import Any
+
+from homeassistant.config_entries import ConfigEntry
+from homeassistant.core import HomeAssistant
+
+from . import HomeAssistantBSBLANData
+from .const import DOMAIN
+
+
+async def async_get_config_entry_diagnostics(
+    hass: HomeAssistant, entry: ConfigEntry
+) -> dict[str, Any]:
+    """Return diagnostics for a config entry."""
+    data: HomeAssistantBSBLANData = hass.data[DOMAIN][entry.entry_id]
+    return {
+        "info": data.info.dict(),
+        "device": data.device.dict(),
+        "state": data.coordinator.data.dict(),
+    }
diff --git a/tests/components/bsblan/fixtures/diagnostics.json b/tests/components/bsblan/fixtures/diagnostics.json
new file mode 100644
index 00000000000..b805a3b0b1b
--- /dev/null
+++ b/tests/components/bsblan/fixtures/diagnostics.json
@@ -0,0 +1,110 @@
+{
+  "info": {
+    "device_identification": {
+      "name": "Gerte-Identifikation",
+      "unit": "",
+      "desc": "",
+      "value": "RVS21.831F/127",
+      "dataType": 7
+    },
+    "controller_family": {
+      "name": "Device family",
+      "unit": "",
+      "desc": "",
+      "value": "211",
+      "dataType": 0
+    },
+    "controller_variant": {
+      "name": "Device variant",
+      "unit": "",
+      "desc": "",
+      "value": "127",
+      "dataType": 0
+    }
+  },
+  "device": {
+    "name": "BSB-LAN",
+    "version": "1.0.38-20200730234859",
+    "MAC": "00:80:41:19:69:90",
+    "uptime": 969402857
+  },
+  "state": {
+    "hvac_mode": {
+      "name": "Operating mode",
+      "unit": "",
+      "desc": "Komfort",
+      "value": "heat",
+      "dataType": 1
+    },
+    "hvac_mode2": {
+      "name": "Operating mode",
+      "unit": "",
+      "desc": "Reduziert",
+      "value": "2",
+      "dataType": 1
+    },
+    "target_temperature": {
+      "name": "Room temperature Comfort setpoint",
+      "unit": "°C",
+      "desc": "",
+      "value": "18.5",
+      "dataType": 0
+    },
+    "target_temperature_high": {
+      "name": "Komfortsollwert Maximum",
+      "unit": "°C",
+      "desc": "",
+      "value": "23.0",
+      "dataType": 0
+    },
+    "target_temperature_low": {
+      "name": "Room temp reduced setpoint",
+      "unit": "°C",
+      "desc": "",
+      "value": "17.0",
+      "dataType": 0
+    },
+    "min_temp": {
+      "name": "Room temp frost protection setpoint",
+      "unit": "°C",
+      "desc": "",
+      "value": "8.0",
+      "dataType": 0
+    },
+    "max_temp": {
+      "name": "Summer/winter changeover temp heat circuit 1",
+      "unit": "°C",
+      "desc": "",
+      "value": "20.0",
+      "dataType": 0
+    },
+    "hvac_action": {
+      "name": "Status heating circuit 1",
+      "unit": "",
+      "desc": "Raumtemp\u2019begrenzung",
+      "value": "122",
+      "dataType": 1
+    },
+    "current_temperature": {
+      "name": "Room temp 1 actual value",
+      "unit": "°C",
+      "desc": "",
+      "value": "18.6",
+      "dataType": 0
+    },
+    "room1_thermostat_mode": {
+      "name": "Raumthermostat 1",
+      "unit": "",
+      "desc": "Kein Bedarf",
+      "value": "0",
+      "dataType": 1
+    },
+    "outside_temperature": {
+      "name": "Outside temp sensor local",
+      "unit": "°C",
+      "desc": "",
+      "value": "6.1",
+      "dataType": 0
+    }
+  }
+}
diff --git a/tests/components/bsblan/test_diagnostics.py b/tests/components/bsblan/test_diagnostics.py
new file mode 100644
index 00000000000..6af6972e577
--- /dev/null
+++ b/tests/components/bsblan/test_diagnostics.py
@@ -0,0 +1,24 @@
+"""Tests for the diagnostics data provided by the BSBLan integration."""
+import json
+
+from aiohttp import ClientSession
+
+from homeassistant.core import HomeAssistant
+
+from tests.common import MockConfigEntry, load_fixture
+from tests.components.diagnostics import get_diagnostics_for_config_entry
+
+
+async def test_diagnostics(
+    hass: HomeAssistant,
+    hass_client: ClientSession,
+    init_integration: MockConfigEntry,
+):
+    """Test diagnostics."""
+
+    diagnostics_fixture = json.loads(load_fixture("bsblan/diagnostics.json"))
+
+    assert (
+        await get_diagnostics_for_config_entry(hass, hass_client, init_integration)
+        == diagnostics_fixture
+    )