diff --git a/litellm/llms/deepseek/chat/transformation.py b/litellm/llms/deepseek/chat/transformation.py
index 5cd8d119542..9cadecb196a 100644
--- a/litellm/llms/deepseek/chat/transformation.py
+++ b/litellm/llms/deepseek/chat/transformation.py
@@ -56,9 +56,12 @@ class DeepSeekChatConfig(OpenAIGPTConfig):
                 # DeepSeek only accepts {"type": "enabled"}, ignore budget_tokens
                 optional_params["thinking"] = {"type": "enabled"}
 
-        # Handle reasoning_effort - map to thinking enabled
-        elif reasoning_effort is not None and reasoning_effort != "none":
-            optional_params["thinking"] = {"type": "enabled"}
+        # Handle reasoning_effort - map to thinking enabled/disabled
+        elif reasoning_effort is not None:
+            if reasoning_effort != "none":
+                optional_params["thinking"] = {"type": "enabled"}
+            else:
+                optional_params["thinking"] = {"type": "disabled"}
 
         return optional_params
 
diff --git a/tests/litellm/llms/deepseek/chat/test_deepseek_chat_transformation.py b/tests/litellm/llms/deepseek/chat/test_deepseek_chat_transformation.py
index a2f45e7188b..e6f2a9ad023 100644
--- a/tests/litellm/llms/deepseek/chat/test_deepseek_chat_transformation.py
+++ b/tests/litellm/llms/deepseek/chat/test_deepseek_chat_transformation.py
@@ -93,8 +93,8 @@ class TestDeepSeekThinkingParams:
 
         assert result["thinking"] == {"type": "enabled"}
 
-    def test_map_reasoning_effort_none_does_not_enable_thinking(self):
-        """Test that reasoning_effort='none' does not enable thinking."""
+    def test_map_reasoning_effort_none_disables_thinking(self):
+        """Test that reasoning_effort='none' sets thinking to disabled."""
         non_default_params = {"reasoning_effort": "none"}
         optional_params = {}
 
@@ -105,7 +105,7 @@ class TestDeepSeekThinkingParams:
             drop_params=False,
         )
 
-        assert "thinking" not in result
+        assert result["thinking"] == {"type": "disabled"}
 
     def test_map_reasoning_effort_null_does_not_enable_thinking(self):
         """Test that reasoning_effort=None does not enable thinking."""