diff --git a/homeassistant/components/monzo/__init__.py b/homeassistant/components/monzo/__init__.py
index e0aa3f3a847..b0a516ae8ad 100644
--- a/homeassistant/components/monzo/__init__.py
+++ b/homeassistant/components/monzo/__init__.py
@@ -6,13 +6,16 @@ import logging
 
 from homeassistant.const import Platform
 from homeassistant.core import HomeAssistant
+from homeassistant.exceptions import ConfigEntryNotReady
 from homeassistant.helpers.aiohttp_client import async_get_clientsession
 from homeassistant.helpers.config_entry_oauth2_flow import (
+    ImplementationUnavailableError,
     OAuth2Session,
     async_get_config_entry_implementation,
 )
 
 from .api import AuthenticatedMonzoAPI
+from .const import DOMAIN
 from .coordinator import MonzoConfigEntry, MonzoCoordinator
 
 _LOGGER = logging.getLogger(__name__)
@@ -39,7 +42,13 @@ async def async_migrate_entry(hass: HomeAssistant, entry: MonzoConfigEntry) -> b
 
 async def async_setup_entry(hass: HomeAssistant, entry: MonzoConfigEntry) -> bool:
     """Set up Monzo from a config entry."""
-    implementation = await async_get_config_entry_implementation(hass, entry)
+    try:
+        implementation = await async_get_config_entry_implementation(hass, entry)
+    except ImplementationUnavailableError as err:
+        raise ConfigEntryNotReady(
+            translation_domain=DOMAIN,
+            translation_key="oauth2_implementation_unavailable",
+        ) from err
 
     session = OAuth2Session(hass, entry, implementation)
 
diff --git a/homeassistant/components/monzo/strings.json b/homeassistant/components/monzo/strings.json
index edb1cd513f6..8f727194ab6 100644
--- a/homeassistant/components/monzo/strings.json
+++ b/homeassistant/components/monzo/strings.json
@@ -50,5 +50,10 @@
         "name": "Total balance"
       }
     }
+  },
+  "exceptions": {
+    "oauth2_implementation_unavailable": {
+      "message": "[%key:common::exceptions::oauth2_implementation_unavailable::message%]"
+    }
   }
 }
diff --git a/tests/components/monzo/test_init.py b/tests/components/monzo/test_init.py
index f255160f1ed..11fe55f3cf1 100644
--- a/tests/components/monzo/test_init.py
+++ b/tests/components/monzo/test_init.py
@@ -7,8 +7,11 @@ from freezegun.api import FrozenDateTimeFactory
 from monzopy import AuthorisationExpiredError
 
 from homeassistant.components.monzo.const import DOMAIN
-from homeassistant.config_entries import SOURCE_REAUTH
+from homeassistant.config_entries import SOURCE_REAUTH, ConfigEntryState
 from homeassistant.core import HomeAssistant
+from homeassistant.helpers.config_entry_oauth2_flow import (
+    ImplementationUnavailableError,
+)
 
 from . import setup_integration
 
@@ -61,3 +64,20 @@ async def test_migrate_entry_minor_version_1_2(hass: HomeAssistant) -> None:
         assert entry.version == 1
         assert entry.minor_version == 2
         assert entry.unique_id == "600"
+
+
+async def test_oauth_implementation_not_available(
+    hass: HomeAssistant,
+    polling_config_entry: MockConfigEntry,
+) -> None:
+    """Test that unavailable OAuth implementation raises ConfigEntryNotReady."""
+    polling_config_entry.add_to_hass(hass)
+
+    with patch(
+        "homeassistant.components.monzo.async_get_config_entry_implementation",
+        side_effect=ImplementationUnavailableError,
+    ):
+        await hass.config_entries.async_setup(polling_config_entry.entry_id)
+        await hass.async_block_till_done()
+
+    assert polling_config_entry.state is ConfigEntryState.SETUP_RETRY