diff --git a/litellm/llms/azure/chat/gpt_5_transformation.py b/litellm/llms/azure/chat/gpt_5_transformation.py
index 209475730f8..2d0ce8b5bce 100644
--- a/litellm/llms/azure/chat/gpt_5_transformation.py
+++ b/litellm/llms/azure/chat/gpt_5_transformation.py
@@ -40,7 +40,11 @@ class AzureOpenAIGPT5Config(AzureOpenAIConfig, OpenAIGPT5Config):
             or optional_params.get("reasoning_effort")
         )
 
-        if reasoning_effort_value == "none":
+        # gpt-5.1 supports reasoning_effort='none', but other gpt-5 models don't
+        # See: https://learn.microsoft.com/en-us/azure/ai-foundry/openai/how-to/reasoning
+        is_gpt_5_1 = self.is_model_gpt_5_1_model(model)
+
+        if reasoning_effort_value == "none" and not is_gpt_5_1:
             if litellm.drop_params is True or (
                 drop_params is not None and drop_params is True
             ):
@@ -54,8 +58,9 @@ class AzureOpenAIGPT5Config(AzureOpenAIConfig, OpenAIGPT5Config):
                 raise UnsupportedParamsError(
                     status_code=400,
                     message=(
-                        "Azure OpenAI does not support reasoning_effort='none'. "
+                        "Azure OpenAI does not support reasoning_effort='none' for this model. "
                         "Supported values are: 'low', 'medium', and 'high'. "
+                        "Note: gpt-5.1 does support reasoning_effort='none'. "
                         "To drop this parameter, set `litellm.drop_params=True` or for proxy:\n\n"
                         "`litellm_settings:\n drop_params: true`\n"
                         "Issue: https://github.com/BerriAI/litellm/issues/16704"
@@ -70,7 +75,8 @@ class AzureOpenAIGPT5Config(AzureOpenAIConfig, OpenAIGPT5Config):
             drop_params=drop_params,
         )
 
-        if result.get("reasoning_effort") == "none":
+        # Only drop reasoning_effort='none' for non-gpt-5.1 models
+        if result.get("reasoning_effort") == "none" and not is_gpt_5_1:
             result.pop("reasoning_effort")
 
         return result
diff --git a/tests/test_litellm/llms/azure/chat/test_azure_gpt5_transformation.py b/tests/test_litellm/llms/azure/chat/test_azure_gpt5_transformation.py
index 3095ff87f5a..91d664c3216 100644
--- a/tests/test_litellm/llms/azure/chat/test_azure_gpt5_transformation.py
+++ b/tests/test_litellm/llms/azure/chat/test_azure_gpt5_transformation.py
@@ -104,34 +104,33 @@ def test_azure_gpt5_codex_series_transform_request(config: AzureOpenAIGPT5Config
 
 # GPT-5.1 temperature handling tests for Azure
 def test_azure_gpt5_1_temperature_with_reasoning_effort_none(config: AzureOpenAIGPT5Config):
-    """Test that Azure GPT-5.1 supports any temperature when reasoning_effort='none' and drop_params=True.
-    
-    Note: Azure OpenAI doesn't support reasoning_effort='none', so it's dropped from the params
-    when drop_params=True. The temperature logic still works correctly because the parent treats
-    missing reasoning_effort the same as 'none' for gpt-5.1.
+    """Test that Azure GPT-5.1 supports any temperature when reasoning_effort='none'.
+
+    Azure OpenAI supports reasoning_effort='none' for gpt-5.1 models.
+    See: https://learn.microsoft.com/en-us/azure/ai-foundry/openai/how-to/reasoning
     """
     params = config.map_openai_params(
         non_default_params={"temperature": 0.5, "reasoning_effort": "none"},
         optional_params={},
         model="azure/gpt-5.1",
-        drop_params=True,
+        drop_params=False,
         api_version="2024-05-01-preview",
     )
     assert params["temperature"] == 0.5
-    # Azure doesn't support reasoning_effort="none", so it should be dropped
-    assert "reasoning_effort" not in params or params.get("reasoning_effort") != "none"
+    # Azure supports reasoning_effort="none" for gpt-5.1
+    assert params.get("reasoning_effort") == "none"
 
 
-def test_azure_gpt5_1_reasoning_effort_none_error_when_drop_params_false(config: AzureOpenAIGPT5Config):
-    """Test that Azure GPT-5.1 raises error for reasoning_effort='none' when drop_params=False."""
-    with pytest.raises(litellm.utils.UnsupportedParamsError):
-        config.map_openai_params(
-            non_default_params={"reasoning_effort": "none"},
-            optional_params={},
-            model="azure/gpt-5.1",
-            drop_params=False,
-            api_version="2024-05-01-preview",
-        )
+def test_azure_gpt5_1_reasoning_effort_none_supported(config: AzureOpenAIGPT5Config):
+    """Test that Azure GPT-5.1 supports reasoning_effort='none' without error."""
+    params = config.map_openai_params(
+        non_default_params={"reasoning_effort": "none"},
+        optional_params={},
+        model="azure/gpt-5.1",
+        drop_params=False,
+        api_version="2024-05-01-preview",
+    )
+    assert params.get("reasoning_effort") == "none"
 
 
 def test_azure_gpt5_1_temperature_without_reasoning_effort(config: AzureOpenAIGPT5Config):
@@ -181,3 +180,27 @@ def test_azure_gpt5_1_series_temperature_handling(config: AzureOpenAIGPT5Config)
     )
     assert params["temperature"] == 0.6
 
+
+def test_azure_gpt5_reasoning_effort_none_error(config: AzureOpenAIGPT5Config):
+    """Test that Azure GPT-5 (non-5.1) raises error for reasoning_effort='none' when drop_params=False."""
+    with pytest.raises(litellm.utils.UnsupportedParamsError):
+        config.map_openai_params(
+            non_default_params={"reasoning_effort": "none"},
+            optional_params={},
+            model="azure/gpt-5",
+            drop_params=False,
+            api_version="2024-05-01-preview",
+        )
+
+
+def test_azure_gpt5_reasoning_effort_none_dropped(config: AzureOpenAIGPT5Config):
+    """Test that Azure GPT-5 (non-5.1) drops reasoning_effort='none' when drop_params=True."""
+    params = config.map_openai_params(
+        non_default_params={"reasoning_effort": "none"},
+        optional_params={},
+        model="azure/gpt-5",
+        drop_params=True,
+        api_version="2024-05-01-preview",
+    )
+    assert "reasoning_effort" not in params or params.get("reasoning_effort") != "none"
+