diff --git a/homeassistant/components/radiotherm/__init__.py b/homeassistant/components/radiotherm/__init__.py
index 091d2bb8005..865e75257ec 100644
--- a/homeassistant/components/radiotherm/__init__.py
+++ b/homeassistant/components/radiotherm/__init__.py
@@ -4,6 +4,7 @@ from __future__ import annotations
 from collections.abc import Coroutine
 from socket import timeout
 from typing import Any, TypeVar
+from urllib.error import URLError
 
 from radiotherm.validate import RadiothermTstatError
 
@@ -31,6 +32,9 @@ async def _async_call_or_raise_not_ready(
     except RadiothermTstatError as ex:
         msg = f"{host} was busy (invalid value returned): {ex}"
         raise ConfigEntryNotReady(msg) from ex
+    except (OSError, URLError) as ex:
+        msg = f"{host} connection error: {ex}"
+        raise ConfigEntryNotReady(msg) from ex
     except timeout as ex:
         msg = f"{host} timed out waiting for a response: {ex}"
         raise ConfigEntryNotReady(msg) from ex
diff --git a/homeassistant/components/radiotherm/config_flow.py b/homeassistant/components/radiotherm/config_flow.py
index 030a3e6c022..97ae2c1be0a 100644
--- a/homeassistant/components/radiotherm/config_flow.py
+++ b/homeassistant/components/radiotherm/config_flow.py
@@ -4,6 +4,7 @@ from __future__ import annotations
 import logging
 from socket import timeout
 from typing import Any
+from urllib.error import URLError
 
 from radiotherm.validate import RadiothermTstatError
 import voluptuous as vol
@@ -29,7 +30,7 @@ async def validate_connection(hass: HomeAssistant, host: str) -> RadioThermInitD
     """Validate the connection."""
     try:
         return await async_get_init_data(hass, host)
-    except (timeout, RadiothermTstatError) as ex:
+    except (timeout, RadiothermTstatError, URLError, OSError) as ex:
         raise CannotConnect(f"Failed to connect to {host}: {ex}") from ex
 
 
diff --git a/homeassistant/components/radiotherm/coordinator.py b/homeassistant/components/radiotherm/coordinator.py
index 4afa2c0662b..91acdee8710 100644
--- a/homeassistant/components/radiotherm/coordinator.py
+++ b/homeassistant/components/radiotherm/coordinator.py
@@ -4,6 +4,7 @@ from __future__ import annotations
 from datetime import timedelta
 import logging
 from socket import timeout
+from urllib.error import URLError
 
 from radiotherm.validate import RadiothermTstatError
 
@@ -38,6 +39,9 @@ class RadioThermUpdateCoordinator(DataUpdateCoordinator[RadioThermUpdate]):
         except RadiothermTstatError as ex:
             msg = f"{self._description} was busy (invalid value returned): {ex}"
             raise UpdateFailed(msg) from ex
+        except (OSError, URLError) as ex:
+            msg = f"{self._description} connection error: {ex}"
+            raise UpdateFailed(msg) from ex
         except timeout as ex:
             msg = f"{self._description}) timed out waiting for a response: {ex}"
             raise UpdateFailed(msg) from ex