diff --git a/homeassistant/components/p1_monitor/diagnostics.py b/homeassistant/components/p1_monitor/diagnostics.py
new file mode 100644
index 00000000000..627d0df767d
--- /dev/null
+++ b/homeassistant/components/p1_monitor/diagnostics.py
@@ -0,0 +1,35 @@
+"""Diagnostics support for P1 Monitor."""
+from __future__ import annotations
+
+from typing import Any
+
+from homeassistant.components.diagnostics import async_redact_data
+from homeassistant.config_entries import ConfigEntry
+from homeassistant.const import CONF_HOST
+from homeassistant.core import HomeAssistant
+
+from . import P1MonitorDataUpdateCoordinator
+from .const import DOMAIN, SERVICE_PHASES, SERVICE_SETTINGS, SERVICE_SMARTMETER
+
+TO_REDACT = {
+    CONF_HOST,
+}
+
+
+async def async_get_config_entry_diagnostics(
+    hass: HomeAssistant, entry: ConfigEntry
+) -> dict[str, Any]:
+    """Return diagnostics for a config entry."""
+    coordinator: P1MonitorDataUpdateCoordinator = hass.data[DOMAIN][entry.entry_id]
+
+    return {
+        "entry": {
+            "title": entry.title,
+            "data": async_redact_data(entry.data, TO_REDACT),
+        },
+        "data": {
+            "smartmeter": coordinator.data[SERVICE_SMARTMETER].__dict__,
+            "phases": coordinator.data[SERVICE_PHASES].__dict__,
+            "settings": coordinator.data[SERVICE_SETTINGS].__dict__,
+        },
+    }
diff --git a/tests/components/p1_monitor/test_diagnostics.py b/tests/components/p1_monitor/test_diagnostics.py
new file mode 100644
index 00000000000..6b97107c353
--- /dev/null
+++ b/tests/components/p1_monitor/test_diagnostics.py
@@ -0,0 +1,59 @@
+"""Tests for the diagnostics data provided by the P1 Monitor integration."""
+from aiohttp import ClientSession
+
+from homeassistant.components.diagnostics import REDACTED
+from homeassistant.core import HomeAssistant
+
+from tests.common import MockConfigEntry
+from tests.components.diagnostics import get_diagnostics_for_config_entry
+
+
+async def test_diagnostics(
+    hass: HomeAssistant,
+    hass_client: ClientSession,
+    init_integration: MockConfigEntry,
+):
+    """Test diagnostics."""
+    assert await get_diagnostics_for_config_entry(
+        hass, hass_client, init_integration
+    ) == {
+        "entry": {
+            "title": "monitor",
+            "data": {
+                "host": REDACTED,
+            },
+        },
+        "data": {
+            "smartmeter": {
+                "gas_consumption": 2273.447,
+                "energy_tariff_period": "high",
+                "power_consumption": 877,
+                "energy_consumption_high": 2770.133,
+                "energy_consumption_low": 4988.071,
+                "power_production": 0,
+                "energy_production_high": 3971.604,
+                "energy_production_low": 1432.279,
+            },
+            "phases": {
+                "voltage_phase_l1": "233.6",
+                "voltage_phase_l2": "0.0",
+                "voltage_phase_l3": "233.0",
+                "current_phase_l1": "1.6",
+                "current_phase_l2": "4.44",
+                "current_phase_l3": "3.51",
+                "power_consumed_phase_l1": 315,
+                "power_consumed_phase_l2": 0,
+                "power_consumed_phase_l3": 624,
+                "power_produced_phase_l1": 0,
+                "power_produced_phase_l2": 0,
+                "power_produced_phase_l3": 0,
+            },
+            "settings": {
+                "gas_consumption_price": "0.64",
+                "energy_consumption_price_high": "0.20522",
+                "energy_consumption_price_low": "0.20522",
+                "energy_production_price_high": "0.20522",
+                "energy_production_price_low": "0.20522",
+            },
+        },
+    }