diff --git a/litellm/llms/azure/passthrough/transformation.py b/litellm/llms/azure/passthrough/transformation.py
index 85647ae02c9..dc71c53e126 100644
--- a/litellm/llms/azure/passthrough/transformation.py
+++ b/litellm/llms/azure/passthrough/transformation.py
@@ -65,6 +65,12 @@ def logged_responses_stream(all_chunks: Sequence[str], logging_obj: Logging) ->
     return terminal_event
 
 
+def without_api_version(api_base: str) -> str:
+    url: Final = httpx.URL(api_base)
+    kept_params: Final = tuple((key, value) for key, value in url.params.multi_items() if key != "api-version")
+    return str(url.copy_with(params=httpx.QueryParams(kept_params)))
+
+
 class AzurePassthroughConfig(BasePassthroughConfig):
     def is_streaming_request(self, endpoint: str, request_data: dict) -> bool:
         return bool(request_data.get("stream"))
@@ -89,8 +95,9 @@ class AzurePassthroughConfig(BasePassthroughConfig):
         native_endpoint: Final = strip_leading_model_segment(routed_endpoint, (model,))
 
         caller_api_version: Final = request_query_params.get("api-version") if request_query_params else None
+        relay_base: Final = without_api_version(base_target_url) if caller_api_version else base_target_url
         complete_url: Final = BaseAzureLLM._get_base_azure_url(
-            api_base=base_target_url,
+            api_base=relay_base,
             litellm_params={**litellm_params, "api_version": caller_api_version or litellm_params.get("api_version")},
             route=native_endpoint,
         )
diff --git a/tests/test_litellm/llms/azure/passthrough/test_azure_passthrough_transformation.py b/tests/test_litellm/llms/azure/passthrough/test_azure_passthrough_transformation.py
index 6e85b0cdca6..a3f5c415417 100644
--- a/tests/test_litellm/llms/azure/passthrough/test_azure_passthrough_transformation.py
+++ b/tests/test_litellm/llms/azure/passthrough/test_azure_passthrough_transformation.py
@@ -369,6 +369,38 @@ def test_azure_passthrough_url_fills_in_the_deployments_api_version_when_the_cal
     assert url.params["api-version"] == "2024-10-21"
 
 
+FULL_URL_API_BASE = (
+    "https://my-resource.openai.azure.com/openai/deployments/gpt-4.1-mini/chat/completions?api-version=2024-10-21"
+)
+
+
+def _full_url_complete_url(request_query_params: dict) -> httpx.URL:
+    url, _ = AzurePassthroughConfig().get_complete_url(
+        api_base=FULL_URL_API_BASE,
+        api_key="key",
+        model="gpt-4.1-mini",
+        endpoint="chat/completions",
+        request_query_params=request_query_params,
+        litellm_params={},
+    )
+    return url
+
+
+def test_azure_passthrough_url_prefers_the_callers_api_version_over_a_full_url_api_bases():
+    url = _full_url_complete_url(request_query_params={"api-version": "2025-04-01-preview"})
+
+    assert str(url) == (
+        "https://my-resource.openai.azure.com/openai/deployments/gpt-4.1-mini/chat/completions"
+        "?api-version=2025-04-01-preview"
+    )
+
+
+def test_azure_passthrough_url_keeps_a_full_url_api_bases_api_version_when_the_caller_sends_none():
+    url = _full_url_complete_url(request_query_params={})
+
+    assert url.params["api-version"] == "2024-10-21"
+
+
 def test_azure_passthrough_url_strips_the_leading_router_model_segment():
     url, _ = AzurePassthroughConfig().get_complete_url(
         api_base="https://my-resource.openai.azure.com",