diff --git a/homeassistant/components/backblaze_b2/__init__.py b/homeassistant/components/backblaze_b2/__init__.py
index 3a8d53f5b2a5..a2767d2f0afa 100644
--- a/homeassistant/components/backblaze_b2/__init__.py
+++ b/homeassistant/components/backblaze_b2/__init__.py
@@ -74,6 +74,12 @@ async def async_setup_entry(hass: HomeAssistant, entry: BackblazeConfigEntry) ->
             translation_domain=DOMAIN,
             translation_key="invalid_bucket_name",
         ) from err
+    except exception.BadRequest as err:
+        raise ConfigEntryNotReady(
+            translation_domain=DOMAIN,
+            translation_key="bad_request",
+            translation_placeholders={"error_message": str(err)},
+        ) from err
     except (
         exception.B2ConnectionError,
         exception.B2RequestTimeout,
diff --git a/homeassistant/components/backblaze_b2/config_flow.py b/homeassistant/components/backblaze_b2/config_flow.py
index 45acf01c8749..fc718505bd18 100644
--- a/homeassistant/components/backblaze_b2/config_flow.py
+++ b/homeassistant/components/backblaze_b2/config_flow.py
@@ -174,6 +174,14 @@ class BackblazeConfigFlow(ConfigFlow, domain=DOMAIN):
                 "Backblaze B2 bucket '%s' does not exist", user_input[CONF_BUCKET]
             )
             errors[CONF_BUCKET] = "invalid_bucket_name"
+        except exception.BadRequest as err:
+            _LOGGER.error(
+                "Backblaze B2 API rejected the request for Key ID '%s': %s",
+                user_input[CONF_KEY_ID],
+                err,
+            )
+            errors["base"] = "bad_request"
+            placeholders["error_message"] = str(err)
         except (
             exception.B2ConnectionError,
             exception.B2RequestTimeout,
diff --git a/homeassistant/components/backblaze_b2/strings.json b/homeassistant/components/backblaze_b2/strings.json
index 15bc4a998d2a..ce8944a7375e 100644
--- a/homeassistant/components/backblaze_b2/strings.json
+++ b/homeassistant/components/backblaze_b2/strings.json
@@ -6,6 +6,7 @@
       "reconfigure_successful": "[%key:common::config_flow::abort::reconfigure_successful%]"
     },
     "error": {
+      "bad_request": "The Backblaze B2 API rejected the request: {error_message}",
       "cannot_connect": "[%key:common::config_flow::error::cannot_connect%]",
       "invalid_bucket_name": "[%key:component::backblaze_b2::exceptions::invalid_bucket_name::message%]",
       "invalid_capability": "[%key:component::backblaze_b2::exceptions::invalid_capability::message%]",
@@ -60,6 +61,9 @@
     }
   },
   "exceptions": {
+    "bad_request": {
+      "message": "The Backblaze B2 API rejected the request: {error_message}"
+    },
     "cannot_connect": {
       "message": "Cannot connect to endpoint"
     },
diff --git a/tests/components/backblaze_b2/test_config_flow.py b/tests/components/backblaze_b2/test_config_flow.py
index 2699576a6e2b..86841deb6a1f 100644
--- a/tests/components/backblaze_b2/test_config_flow.py
+++ b/tests/components/backblaze_b2/test_config_flow.py
@@ -177,6 +177,16 @@ async def test_already_configured(
             "cannot_connect",
             "base",
         ),
+        (
+            "bad_request",
+            {
+                "patch": "b2sdk.v2.RawSimulator.authorize_account",
+                "exception": exception.BadRequest,
+                "args": ["test", "bad_request"],
+            },
+            "bad_request",
+            "base",
+        ),
         (
             "unknown_error",
             {
@@ -252,6 +262,11 @@ async def test_config_flow_errors(
             "brand_name": "Backblaze B2",
             "allowed_prefix": "test/",
         }
+    elif error_type == "bad_request":
+        assert result.get("description_placeholders") == {
+            "brand_name": "Backblaze B2",
+            "error_message": "test (bad_request)",
+        }
 
 
 @pytest.mark.parametrize(
diff --git a/tests/components/backblaze_b2/test_init.py b/tests/components/backblaze_b2/test_init.py
index 533364381475..2a15e0bd5c4c 100644
--- a/tests/components/backblaze_b2/test_init.py
+++ b/tests/components/backblaze_b2/test_init.py
@@ -57,6 +57,7 @@ async def test_setup_entry_invalid_auth(
         (exception.RestrictedBucket("testBucket"), ConfigEntryState.SETUP_RETRY),
         (exception.NonExistentBucket(), ConfigEntryState.SETUP_RETRY),
         (exception.ConnectionReset(), ConfigEntryState.SETUP_RETRY),
+        (exception.BadRequest("test", "bad_request"), ConfigEntryState.SETUP_RETRY),
         (exception.MissingAccountData("key"), ConfigEntryState.SETUP_ERROR),
     ],
 )