diff --git a/homeassistant/components/thread/diagnostics.py b/homeassistant/components/thread/diagnostics.py
index b945f818d00..eb1e2a5ef68 100644
--- a/homeassistant/components/thread/diagnostics.py
+++ b/homeassistant/components/thread/diagnostics.py
@@ -17,9 +17,8 @@ some of their thread accessories can't be pinged, but it's still a thread proble
 
 from __future__ import annotations
 
-from typing import Any, TypedDict
+from typing import TYPE_CHECKING, Any, TypedDict
 
-from pyroute2 import NDB  # pylint: disable=no-name-in-module
 from python_otbr_api.tlv_parser import MeshcopTLVType
 
 from homeassistant.components import zeroconf
@@ -29,6 +28,9 @@ from homeassistant.core import HomeAssistant
 from .dataset_store import async_get_store
 from .discovery import async_read_zeroconf_cache
 
+if TYPE_CHECKING:
+    from pyroute2 import NDB  # pylint: disable=no-name-in-module
+
 
 class Neighbour(TypedDict):
     """A neighbour cache entry (ip neigh)."""
@@ -67,58 +69,69 @@ class Network(TypedDict):
     unexpected_routers: set[str]
 
 
-def _get_possible_thread_routes() -> (
-    tuple[dict[str, dict[str, Route]], dict[str, set[str]]]
-):
+def _get_possible_thread_routes(
+    ndb: NDB,
+) -> tuple[dict[str, dict[str, Route]], dict[str, set[str]]]:
     # Build a list of possible thread routes
     # Right now, this is ipv6 /64's that have a gateway
     # We cross reference with zerconf data to confirm which via's are known border routers
     routes: dict[str, dict[str, Route]] = {}
     reverse_routes: dict[str, set[str]] = {}
 
-    with NDB() as ndb:
-        for record in ndb.routes:
-            # Limit to IPV6 routes
-            if record.family != 10:
-                continue
-            # Limit to /64 prefixes
-            if record.dst_len != 64:
-                continue
-            # Limit to routes with a via
-            if not record.gateway and not record.nh_gateway:
-                continue
-            gateway = record.gateway or record.nh_gateway
-            route = routes.setdefault(gateway, {})
-            route[record.dst] = {
-                "metrics": record.metrics,
-                "priority": record.priority,
-                # NM creates "nexthop" routes - a single route with many via's
-                # Kernel creates many routes with a single via
-                "is_nexthop": record.nh_gateway is not None,
-            }
-            reverse_routes.setdefault(record.dst, set()).add(gateway)
+    for record in ndb.routes:
+        # Limit to IPV6 routes
+        if record.family != 10:
+            continue
+        # Limit to /64 prefixes
+        if record.dst_len != 64:
+            continue
+        # Limit to routes with a via
+        if not record.gateway and not record.nh_gateway:
+            continue
+        gateway = record.gateway or record.nh_gateway
+        route = routes.setdefault(gateway, {})
+        route[record.dst] = {
+            "metrics": record.metrics,
+            "priority": record.priority,
+            # NM creates "nexthop" routes - a single route with many via's
+            # Kernel creates many routes with a single via
+            "is_nexthop": record.nh_gateway is not None,
+        }
+        reverse_routes.setdefault(record.dst, set()).add(gateway)
     return routes, reverse_routes
 
 
-def _get_neighbours() -> dict[str, Neighbour]:
-    neighbours: dict[str, Neighbour] = {}
-
-    with NDB() as ndb:
-        for record in ndb.neighbours:
-            neighbours[record.dst] = {
-                "lladdr": record.lladdr,
-                "state": record.state,
-                "probes": record.probes,
-            }
-
+def _get_neighbours(ndb: NDB) -> dict[str, Neighbour]:
+    # Build a list of neighbours
+    neighbours: dict[str, Neighbour] = {
+        record.dst: {
+            "lladdr": record.lladdr,
+            "state": record.state,
+            "probes": record.probes,
+        }
+        for record in ndb.neighbours
+    }
     return neighbours
 
 
+def _get_routes_and_neighbors():
+    """Get the routes and neighbours from pyroute2."""
+    # Import in the executor since import NDB can take a while
+    from pyroute2 import (  # pylint: disable=no-name-in-module, import-outside-toplevel
+        NDB,
+    )
+
+    with NDB() as ndb:  # pylint: disable=not-callable
+        routes, reverse_routes = _get_possible_thread_routes(ndb)
+        neighbours = _get_neighbours(ndb)
+
+    return routes, reverse_routes, neighbours
+
+
 async def async_get_config_entry_diagnostics(
     hass: HomeAssistant, entry: ConfigEntry
 ) -> dict[str, Any]:
     """Return diagnostics for all known thread networks."""
-
     networks: dict[str, Network] = {}
 
     # Start with all networks that HA knows about
@@ -140,13 +153,12 @@ async def async_get_config_entry_diagnostics(
 
     # Find all routes currently act that might be thread related, so we can match them to
     # border routers as we process the zeroconf data.
-    routes, reverse_routes = await hass.async_add_executor_job(
-        _get_possible_thread_routes
+    #
+    # Also find all neighbours
+    routes, reverse_routes, neighbours = await hass.async_add_executor_job(
+        _get_routes_and_neighbors
     )
 
-    # Find all neighbours
-    neighbours = await hass.async_add_executor_job(_get_neighbours)
-
     aiozc = await zeroconf.async_get_async_instance(hass)
     for data in async_read_zeroconf_cache(aiozc):
         if not data.extended_pan_id:
diff --git a/tests/components/thread/test_diagnostics.py b/tests/components/thread/test_diagnostics.py
index 1006fa374c3..a551315205b 100644
--- a/tests/components/thread/test_diagnostics.py
+++ b/tests/components/thread/test_diagnostics.py
@@ -133,9 +133,7 @@ class MockNeighbour:
 @pytest.fixture
 def ndb() -> Mock:
     """Prevent NDB poking the OS route tables."""
-    with patch(
-        "homeassistant.components.thread.diagnostics.NDB"
-    ) as ndb, ndb() as instance:
+    with patch("pyroute2.NDB") as ndb, ndb() as instance:
         instance.neighbours = []
         instance.routes = []
         yield instance