diff --git a/homeassistant/components/unifi_discovery/discovery.py b/homeassistant/components/unifi_discovery/discovery.py
index 6bd8a4b24cdf..5a4174a4f6b5 100644
--- a/homeassistant/components/unifi_discovery/discovery.py
+++ b/homeassistant/components/unifi_discovery/discovery.py
@@ -2,7 +2,8 @@
 
 from __future__ import annotations
 
-from dataclasses import asdict
+from collections.abc import Mapping
+from dataclasses import fields
 from datetime import timedelta
 import logging
 from typing import Any
@@ -24,6 +25,24 @@ DISCOVERY_INTERVAL = timedelta(minutes=60)
 DATA_DISCOVERY_STARTED: HassKey[bool] = HassKey(DOMAIN)
 
 
+def _device_to_dict(device: UnifiDevice) -> dict[str, Any]:
+    """Convert a UnifiDevice to a plain dict.
+
+    Avoid dataclasses.asdict() because it calls copy.deepcopy() on non-builtin
+    types.  On Python 3.14+ deepcopy cannot pickle mappingproxy objects, and
+    Enum members (used as dict keys in ``services``) internally reference
+    ``__members__`` which is a mappingproxy.  This causes asdict() to crash
+    with ``TypeError: cannot pickle 'mappingproxy' object``.
+    """
+    data: dict[str, Any] = {}
+    for f in fields(device):
+        value = getattr(device, f.name)
+        if isinstance(value, Mapping):
+            value = dict(value)
+        data[f.name] = value
+    return data
+
+
 @callback
 def async_start_discovery(hass: HomeAssistant) -> None:
     """Start discovery of UniFi devices."""
@@ -74,5 +93,5 @@ def async_trigger_discovery(
                     hass,
                     domain,
                     context={"source": config_entries.SOURCE_INTEGRATION_DISCOVERY},
-                    data=asdict(device),
+                    data=_device_to_dict(device),
                 )
diff --git a/tests/components/unifi_discovery/__init__.py b/tests/components/unifi_discovery/__init__.py
index c068a3ba1e0e..08916c8aa011 100644
--- a/tests/components/unifi_discovery/__init__.py
+++ b/tests/components/unifi_discovery/__init__.py
@@ -2,6 +2,7 @@
 
 from collections.abc import Generator
 from contextlib import contextmanager
+from types import MappingProxyType
 from unittest.mock import AsyncMock, MagicMock, patch
 
 from unifi_discovery import AIOUnifiScanner, UnifiDevice, UnifiService
@@ -30,6 +31,21 @@ UNIFI_DISCOVERY_NO_MAC = UnifiDevice(
     direct_connect_domain=DIRECT_CONNECT_DOMAIN,
 )
 
+# In production the crash happens because asdict() deep-copies Enum keys in
+# the services dict, and on Python 3.14+ deepcopy traverses into
+# Enum.__members__ (a mappingproxy) which cannot be pickled.  Whether
+# deepcopy(enum) actually fails depends on the specific CPython build, so
+# we force the error reliably by using MappingProxyType directly as the
+# services value — deepcopy always fails on it.
+UNIFI_DISCOVERY_MAPPINGPROXY_SERVICES = UnifiDevice(
+    source_ip=DEVICE_IP_ADDRESS,
+    hw_addr=DEVICE_MAC_ADDRESS,
+    platform=DEVICE_HOSTNAME,
+    hostname=DEVICE_HOSTNAME,
+    services=MappingProxyType({UnifiService.Protect: True}),
+    direct_connect_domain=DIRECT_CONNECT_DOMAIN,
+)
+
 
 def _patch_discovery(
     device: UnifiDevice | None = None, no_device: bool = False
diff --git a/tests/components/unifi_discovery/test_init.py b/tests/components/unifi_discovery/test_init.py
index e76511562c31..80207bd81ef5 100644
--- a/tests/components/unifi_discovery/test_init.py
+++ b/tests/components/unifi_discovery/test_init.py
@@ -7,7 +7,11 @@ from homeassistant.components.unifi_discovery.const import DOMAIN
 from homeassistant.core import HomeAssistant
 from homeassistant.setup import async_setup_component
 
-from . import UNIFI_DISCOVERY_NO_MAC, _patch_discovery
+from . import (
+    UNIFI_DISCOVERY_MAPPINGPROXY_SERVICES,
+    UNIFI_DISCOVERY_NO_MAC,
+    _patch_discovery,
+)
 
 
 async def test_setup_starts_discovery(hass: HomeAssistant) -> None:
@@ -54,3 +58,20 @@ async def test_dependency_loads_discovery(
     flows = hass.config_entries.flow.async_progress_by_handler("unifiprotect")
     assert len(flows) == 1
     assert flows[0]["context"]["source"] == config_entries.SOURCE_INTEGRATION_DISCOVERY
+
+
+async def test_discovery_does_not_deepcopy_device(hass: HomeAssistant) -> None:
+    """Test discovery works without deepcopy.
+
+    In production asdict() deep-copies Enum keys in the services dict which
+    can crash on Python 3.14+ because Enum.__members__ is a mappingproxy that
+    cannot be pickled.  We force the crash reliably by using MappingProxyType
+    as the services value.
+    """
+    with _patch_discovery(device=UNIFI_DISCOVERY_MAPPINGPROXY_SERVICES):
+        assert await async_setup_component(hass, DOMAIN, {})
+        await hass.async_block_till_done(wait_background_tasks=True)
+
+    flows = hass.config_entries.flow.async_progress_by_handler("unifiprotect")
+    assert len(flows) == 1
+    assert flows[0]["context"]["source"] == config_entries.SOURCE_INTEGRATION_DISCOVERY