diff --git a/homeassistant/components/pegel_online/diagnostics.py b/homeassistant/components/pegel_online/diagnostics.py
new file mode 100644
index 00000000000..b68437c5ee7
--- /dev/null
+++ b/homeassistant/components/pegel_online/diagnostics.py
@@ -0,0 +1,21 @@
+"""Diagnostics support for pegel_online."""
+
+from __future__ import annotations
+
+from typing import Any
+
+from homeassistant.core import HomeAssistant
+
+from . import PegelOnlineConfigEntry
+
+
+async def async_get_config_entry_diagnostics(
+    hass: HomeAssistant, entry: PegelOnlineConfigEntry
+) -> dict[str, Any]:
+    """Return diagnostics for a config entry."""
+    coordinator = entry.runtime_data
+
+    return {
+        "entry": entry.as_dict(),
+        "data": coordinator.data,
+    }
diff --git a/tests/components/pegel_online/snapshots/test_diagnostics.ambr b/tests/components/pegel_online/snapshots/test_diagnostics.ambr
new file mode 100644
index 00000000000..1e55805f867
--- /dev/null
+++ b/tests/components/pegel_online/snapshots/test_diagnostics.ambr
@@ -0,0 +1,39 @@
+# serializer version: 1
+# name: test_entry_diagnostics
+  dict({
+    'data': dict({
+      'air_temperature': None,
+      'clearance_height': None,
+      'oxygen_level': None,
+      'ph_value': None,
+      'water_flow': dict({
+        'uom': 'm³/s',
+        'value': 88.4,
+      }),
+      'water_level': dict({
+        'uom': 'cm',
+        'value': 62,
+      }),
+      'water_speed': None,
+      'water_temperature': None,
+    }),
+    'entry': dict({
+      'data': dict({
+        'station': '70272185-xxxx-xxxx-xxxx-43bea330dcae',
+      }),
+      'disabled_by': None,
+      'discovery_keys': dict({
+      }),
+      'domain': 'pegel_online',
+      'minor_version': 1,
+      'options': dict({
+      }),
+      'pref_disable_new_entities': False,
+      'pref_disable_polling': False,
+      'source': 'user',
+      'title': 'Mock Title',
+      'unique_id': '70272185-xxxx-xxxx-xxxx-43bea330dcae',
+      'version': 1,
+    }),
+  })
+# ---
diff --git a/tests/components/pegel_online/test_diagnostics.py b/tests/components/pegel_online/test_diagnostics.py
new file mode 100644
index 00000000000..220f244b751
--- /dev/null
+++ b/tests/components/pegel_online/test_diagnostics.py
@@ -0,0 +1,44 @@
+"""Test pegel_online diagnostics."""
+
+from unittest.mock import patch
+
+from syrupy import SnapshotAssertion
+from syrupy.filters import props
+
+from homeassistant.components.pegel_online.const import CONF_STATION, DOMAIN
+from homeassistant.core import HomeAssistant
+
+from . import PegelOnlineMock
+from .const import (
+    MOCK_CONFIG_ENTRY_DATA_DRESDEN,
+    MOCK_STATION_DETAILS_DRESDEN,
+    MOCK_STATION_MEASUREMENT_DRESDEN,
+)
+
+from tests.common import MockConfigEntry
+from tests.components.diagnostics import get_diagnostics_for_config_entry
+from tests.typing import ClientSessionGenerator
+
+
+async def test_entry_diagnostics(
+    hass: HomeAssistant,
+    hass_client: ClientSessionGenerator,
+    snapshot: SnapshotAssertion,
+) -> None:
+    """Test config entry diagnostics."""
+    entry = MockConfigEntry(
+        domain=DOMAIN,
+        data=MOCK_CONFIG_ENTRY_DATA_DRESDEN,
+        unique_id=MOCK_CONFIG_ENTRY_DATA_DRESDEN[CONF_STATION],
+    )
+    entry.add_to_hass(hass)
+    with patch("homeassistant.components.pegel_online.PegelOnline") as pegelonline:
+        pegelonline.return_value = PegelOnlineMock(
+            station_details=MOCK_STATION_DETAILS_DRESDEN,
+            station_measurements=MOCK_STATION_MEASUREMENT_DRESDEN,
+        )
+        assert await hass.config_entries.async_setup(entry.entry_id)
+    await hass.async_block_till_done()
+
+    result = await get_diagnostics_for_config_entry(hass, hass_client, entry)
+    assert result == snapshot(exclude=props("entry_id", "created_at", "modified_at"))