diff --git a/autogen/oai/client.py b/autogen/oai/client.py
index e8ae0602e0..a814c1c9c8 100644
--- a/autogen/oai/client.py
+++ b/autogen/oai/client.py
@@ -295,10 +295,58 @@ def _is_agent_name_error_message(message: str) -> bool:
         pattern = re.compile(r"Invalid 'messages\[\d+\]\.name': string does not match pattern.")
         return True if pattern.match(message) else False
 
+    @staticmethod
+    def _move_system_message_to_beginning(messages: list[dict[str, Any]]) -> None:
+        for msg in messages:
+            if msg["role"] == "system":
+                messages.insert(0, messages.pop(messages.index(msg)))
+                break
+
+    @staticmethod
+    def _patch_messages_for_deepseek_reasoner(**kwargs: Any) -> Any:
+        if (
+            "model" not in kwargs
+            or kwargs["model"] != "deepseek-reasoner"
+            or "messages" not in kwargs
+            or len(kwargs["messages"]) == 0
+        ):
+            return kwargs
+
+        # The system message of deepseek-reasoner must be put on the beginning of the message sequence.
+        OpenAIClient._move_system_message_to_beginning(kwargs["messages"])
+
+        new_messages = []
+        previous_role = None
+        for message in kwargs["messages"]:
+            if "role" in message:
+                current_role = message["role"]
+
+                # This model requires alternating roles
+                if current_role == previous_role:
+                    # Swap the role
+                    if current_role == "user":
+                        message["role"] = "assistant"
+                    elif current_role == "assistant":
+                        message["role"] = "user"
+
+                previous_role = message["role"]
+
+            new_messages.append(message)
+
+        # The last message of deepseek-reasoner must be a user message
+        # , or an assistant message with prefix mode on (but this is supported only for beta api)
+        if new_messages[-1]["role"] != "user":
+            new_messages.append({"role": "user", "content": "continue"})
+
+        kwargs["messages"] = new_messages
+
+        return kwargs
+
     @staticmethod
     def _handle_openai_bad_request_error(func: Callable[..., Any]) -> Callable[..., Any]:
         def wrapper(*args: Any, **kwargs: Any):
             try:
+                kwargs = OpenAIClient._patch_messages_for_deepseek_reasoner(**kwargs)
                 return func(*args, **kwargs)
             except openai.BadRequestError as e:
                 response_json = e.response.json()
diff --git a/test/agentchat/test_conversable_agent.py b/test/agentchat/test_conversable_agent.py
index 4be2fa0a0e..369b48c3e1 100755
--- a/test/agentchat/test_conversable_agent.py
+++ b/test/agentchat/test_conversable_agent.py
@@ -1608,6 +1608,26 @@ def login(
     mock.assert_called_once()
 
 
+@pytest.mark.deepseek
+def test_conversable_agent_with_deepseek_reasoner(
+    credentials_deepseek_reasoner: Credentials,
+) -> None:
+    agent = ConversableAgent(
+        name="agent",
+        llm_config=credentials_deepseek_reasoner.llm_config,
+    )
+
+    user_proxy = UserProxyAgent(
+        name="user_proxy_1",
+        human_input_mode="NEVER",
+    )
+
+    result = user_proxy.initiate_chat(
+        agent, message="Hello, how are you?", summary_method="reflection_with_llm", max_turns=2
+    )
+    assert isinstance(result.summary, str)
+
+
 if __name__ == "__main__":
     # test_trigger()
     # test_context()
diff --git a/test/agentchat/test_groupchat.py b/test/agentchat/test_groupchat.py
index 18869acbed..23850bcd4d 100755
--- a/test/agentchat/test_groupchat.py
+++ b/test/agentchat/test_groupchat.py
@@ -10,6 +10,7 @@
 import io
 import json
 import logging
+import tempfile
 from types import SimpleNamespace
 from typing import Any, Optional
 from unittest import mock
@@ -21,6 +22,8 @@
 from autogen.agentchat.contrib.capabilities import transform_messages, transforms
 from autogen.exception_utils import AgentNameConflict, UndefinedNextAgent
 
+from ..conftest import Credentials
+
 
 def test_func_call_groupchat():
     agent1 = autogen.ConversableAgent(
@@ -2181,6 +2184,51 @@ def test_manager_resume_message_assignment():
     assert list(agent_a.chat_messages.values())[0] == prev_messages[:-1]
 
 
+@pytest.mark.deepseek
+def test_groupchat_with_deepseek_reasoner(
+    credentials_gpt_4o_mini: Credentials,
+    credentials_deepseek_reasoner: Credentials,
+) -> None:
+    with tempfile.TemporaryDirectory() as tmp_dir:
+        user_proxy = autogen.UserProxyAgent(
+            "user_proxy",
+            human_input_mode="NEVER",
+            code_execution_config={"work_dir": tmp_dir, "use_docker": False},
+        )
+
+        supervisor = autogen.AssistantAgent(
+            "supervisor",
+            llm_config={
+                "config_list": credentials_deepseek_reasoner.config_list,
+            },
+        )
+
+        assistant = autogen.AssistantAgent(
+            "assistant",
+            llm_config={
+                "config_list": credentials_deepseek_reasoner.config_list,
+            },
+        )
+
+        groupchat = autogen.GroupChat(
+            agents=[user_proxy, supervisor, assistant],
+            messages=["A group chat"],
+            max_round=5,
+        )
+
+        manager = autogen.GroupChatManager(
+            groupchat=groupchat,
+            llm_config={
+                "config_list": credentials_gpt_4o_mini.config_list,
+            },
+        )
+
+        result = user_proxy.initiate_chat(
+            manager, message="""Give me some info about the stock market""", summary_method="reflection_with_llm"
+        )
+        assert isinstance(result.summary, str)
+
+
 if __name__ == "__main__":
     # test_func_call_groupchat()
     # test_broadcast()
diff --git a/test/conftest.py b/test/conftest.py
index 2b946d2605..90cb3becff 100644
--- a/test/conftest.py
+++ b/test/conftest.py
@@ -178,16 +178,25 @@ def get_credentials(
 
 
 def get_config_list_from_env(
-    env_var_name: str, model: str, api_type: str, filter_dict: Optional[dict[str, Any]] = None, temperature: float = 0.0
+    env_var_name: str,
+    model: str,
+    api_type: str,
+    filter_dict: Optional[dict[str, Any]] = None,
+    temperature: float = 0.0,
 ) -> list[dict[str, Any]]:
     if env_var_name in os.environ:
         api_key = os.environ[env_var_name]
         return [{"api_key": api_key, "model": model, **filter_dict, "api_type": api_type}]  # type: ignore[dict-item]
+
     return []
 
 
 def get_llm_credentials(
-    env_var_name: str, model: str, api_type: str, filter_dict: Optional[dict[str, Any]] = None, temperature: float = 0.0
+    env_var_name: str,
+    model: str,
+    api_type: str,
+    filter_dict: Optional[dict[str, Any]] = None,
+    temperature: float = 0.0,
 ) -> Credentials:
     credentials = get_credentials(filter_dict, temperature, fail_if_empty=False)
     config_list = credentials.config_list if credentials else []
@@ -301,7 +310,7 @@ def credentials_deepseek_reasoner() -> Credentials:
         "DEEPSEEK_API_KEY",
         model="deepseek-reasoner",
         api_type="deepseek",
-        filter_dict={"tags": ["deepseek-reasoner"]},
+        filter_dict={"tags": ["deepseek-reasoner"], "base_url": "https://api.deepseek.com/v1"},
     )
 
 
diff --git a/test/oai/test_client.py b/test/oai/test_client.py
index 774be3c335..3f62cee7ca 100755
--- a/test/oai/test_client.py
+++ b/test/oai/test_client.py
@@ -6,6 +6,7 @@
 # SPDX-License-Identifier: MIT
 #!/usr/bin/env python3 -m pytest
 
+import copy
 import os
 import shutil
 import time
@@ -342,6 +343,95 @@ def raise_bad_request_error(error_message: str) -> None:
                 wrapped_raise_bad_request_error(error_message=error_message)
 
 
+class TestDeepSeekPatch:
+    @pytest.mark.parametrize(
+        "messages, expected_messages",
+        [
+            (
+                [
+                    {"role": "system", "content": "You are an AG2 Agent."},
+                    {"role": "user", "content": "Help me with my problem."},
+                ],
+                [
+                    {"role": "system", "content": "You are an AG2 Agent."},
+                    {"role": "user", "content": "Help me with my problem."},
+                ],
+            ),
+            (
+                [
+                    {"role": "user", "content": "You are an AG2 Agent."},
+                    {"role": "user", "content": "Help me with my problem."},
+                ],
+                [
+                    {"role": "user", "content": "You are an AG2 Agent."},
+                    {"role": "user", "content": "Help me with my problem."},
+                ],
+            ),
+            (
+                [
+                    {"role": "assistant", "content": "Help me with my problem."},
+                    {"role": "system", "content": "You are an AG2 Agent."},
+                ],
+                [
+                    {"role": "system", "content": "You are an AG2 Agent."},
+                    {"role": "assistant", "content": "Help me with my problem."},
+                ],
+            ),
+            (
+                [
+                    {"role": "assistant", "content": "Help me with my problem."},
+                    {"role": "system", "content": "You are an AG2 Agent."},
+                    {"role": "user", "content": "Help me with my problem."},
+                ],
+                [
+                    {"role": "system", "content": "You are an AG2 Agent."},
+                    {"role": "assistant", "content": "Help me with my problem."},
+                    {"role": "user", "content": "Help me with my problem."},
+                ],
+            ),
+        ],
+    )
+    def test_move_system_message_to_beginning(
+        self, messages: list[dict[str, str]], expected_messages: list[dict[str, str]]
+    ) -> None:
+        OpenAIClient._move_system_message_to_beginning(messages)
+        assert messages == expected_messages
+
+    @pytest.mark.parametrize(
+        "model, should_patch",
+        [
+            ("deepseek-reasoner", True),
+            ("deepseek", False),
+            ("something-else", False),
+        ],
+    )
+    def test_patch_messages_for_deepseek_reasoner(self, model: str, should_patch: bool) -> None:
+        kwargs = {
+            "messages": [
+                {"role": "user", "content": "You are an AG2 Agent."},
+                {"role": "system", "content": "You are an AG2 Agent System."},
+                {"role": "user", "content": "Help me with my problem."},
+            ],
+            "model": model,
+        }
+
+        if should_patch:
+            expected_kwargs = {
+                "messages": [
+                    {"role": "system", "content": "You are an AG2 Agent System."},
+                    {"role": "user", "content": "You are an AG2 Agent."},
+                    {"role": "assistant", "content": "Help me with my problem."},
+                    {"role": "user", "content": "continue"},
+                ],
+                "model": "deepseek-reasoner",
+            }
+        else:
+            expected_kwargs = copy.deepcopy(kwargs)
+
+        kwargs = OpenAIClient._patch_messages_for_deepseek_reasoner(**kwargs)
+        assert kwargs == expected_kwargs
+
+
 class TestO1:
     @pytest.fixture
     def mock_oai_client(self, mock_credentials: Credentials) -> OpenAIClient:
diff --git a/test/test_conftest.py b/test/test_conftest.py
index 0700d33da2..28da381d12 100644
--- a/test/test_conftest.py
+++ b/test/test_conftest.py
@@ -32,9 +32,3 @@ def test_credentials_from_test_param_fixture(
         assert first_config["api_type"] == "anthropic"
     else:
         assert False, f"Unknown LLM fixture: {current_llm}"
-
-
-@pytest.mark.deepseek
-def test_credentials_deepseek_reasoner_api_key_is_set(credentials_deepseek_reasoner: Credentials) -> None:
-    assert len(credentials_deepseek_reasoner.config_list) > 0
-    assert credentials_deepseek_reasoner.config_list[0]["api_key"] is not None