diff --git a/autogen/agentchat/conversable_agent.py b/autogen/agentchat/conversable_agent.py
index 1f1b2ff489f7..86ef3db0d295 100644
--- a/autogen/agentchat/conversable_agent.py
+++ b/autogen/agentchat/conversable_agent.py
@@ -136,6 +136,24 @@ def __init__(
             else (lambda x: content_str(x.get("content")) == "TERMINATE")
         )
 
+        if llm_config is None:
+            raise ValueError("Please specify the value for 'llm_config'.")
+
+        if isinstance(llm_config, dict):
+            config_list = None
+            if "config_list" in llm_config:
+                config_list = llm_config["config_list"]
+            if config_list is None or len(config_list) == 0:
+                raise ValueError("Please specify at least one configuration in 'llm_config'.")
+
+            # We know that there's at least one entry in the configuration.
+            # Verify that model is specified as well.
+            model = None
+            if "model" in llm_config["config_list"][0]:
+                model = llm_config["config_list"][0]["model"]
+            if model is None or len(model) == 0:
+                raise ValueError("Please specify a value for the 'model' in 'llm_config'.")
+
         if llm_config is False:
             self.llm_config = False
             self.client = None
diff --git a/test/agentchat/test_conversable_agent.py b/test/agentchat/test_conversable_agent.py
index a10b1a0e3a07..a07897a418eb 100644
--- a/test/agentchat/test_conversable_agent.py
+++ b/test/agentchat/test_conversable_agent.py
@@ -474,7 +474,7 @@ async def test_a_generate_reply_raises_on_messages_and_sender_none(conversable_a
 def test_update_function_signature_and_register_functions() -> None:
     with pytest.MonkeyPatch.context() as mp:
         mp.setenv("OPENAI_API_KEY", MOCK_OPEN_AI_API_KEY)
-        agent = ConversableAgent(name="agent", llm_config={})
+        agent = ConversableAgent(name="agent", llm_config={"config_list": [{"model": "gpt-4", "api_key": ""}]})
 
         def exec_python(cell: str) -> None:
             pass
@@ -618,9 +618,9 @@ def get_origin(d: Dict[str, Callable[..., Any]]) -> Dict[str, Callable[..., Any]
 def test_register_for_llm():
     with pytest.MonkeyPatch.context() as mp:
         mp.setenv("OPENAI_API_KEY", MOCK_OPEN_AI_API_KEY)
-        agent3 = ConversableAgent(name="agent3", llm_config={"config_list": []})
-        agent2 = ConversableAgent(name="agent2", llm_config={"config_list": []})
-        agent1 = ConversableAgent(name="agent1", llm_config={"config_list": []})
+        agent3 = ConversableAgent(name="agent3", llm_config={"config_list": [{"model": "gpt-4", "api_key": ""}]})
+        agent2 = ConversableAgent(name="agent2", llm_config={"config_list": [{"model": "gpt-4", "api_key": ""}]})
+        agent1 = ConversableAgent(name="agent1", llm_config={"config_list": [{"model": "gpt-4", "api_key": ""}]})
 
         @agent3.register_for_llm()
         @agent2.register_for_llm(name="python")
@@ -691,9 +691,9 @@ async def exec_sh(script: Annotated[str, "Valid shell script to execute."]) -> s
 def test_register_for_llm_api_style_function():
     with pytest.MonkeyPatch.context() as mp:
         mp.setenv("OPENAI_API_KEY", MOCK_OPEN_AI_API_KEY)
-        agent3 = ConversableAgent(name="agent3", llm_config={"config_list": []})
-        agent2 = ConversableAgent(name="agent2", llm_config={"config_list": []})
-        agent1 = ConversableAgent(name="agent1", llm_config={"config_list": []})
+        agent3 = ConversableAgent(name="agent3", llm_config={"config_list": [{"model": "gpt-4", "api_key": ""}]})
+        agent2 = ConversableAgent(name="agent2", llm_config={"config_list": [{"model": "gpt-4", "api_key": ""}]})
+        agent1 = ConversableAgent(name="agent1", llm_config={"config_list": [{"model": "gpt-4", "api_key": ""}]})
 
         @agent3.register_for_llm(api_style="function")
         @agent2.register_for_llm(name="python", api_style="function")
@@ -762,7 +762,7 @@ async def exec_sh(script: Annotated[str, "Valid shell script to execute."]) -> s
 def test_register_for_llm_without_description():
     with pytest.MonkeyPatch.context() as mp:
         mp.setenv("OPENAI_API_KEY", MOCK_OPEN_AI_API_KEY)
-        agent = ConversableAgent(name="agent", llm_config={})
+        agent = ConversableAgent(name="agent", llm_config={"config_list": [{"model": "gpt-4", "api_key": ""}]})
 
         with pytest.raises(ValueError) as e:
 
@@ -774,25 +774,33 @@ def exec_python(cell: Annotated[str, "Valid Python cell to execute."]) -> str:
 
 
 def test_register_for_llm_without_LLM():
-    with pytest.MonkeyPatch.context() as mp:
-        mp.setenv("OPENAI_API_KEY", MOCK_OPEN_AI_API_KEY)
-        agent = ConversableAgent(name="agent", llm_config=None)
-        agent.llm_config = None
-        assert agent.llm_config is None
+    try:
+        ConversableAgent(name="agent", llm_config=None)
+        assert False, "Expected ConversableAgent to throw ValueError."
+    except ValueError as e:
+        assert e.args[0] == "Please specify the value for 'llm_config'."
 
-        with pytest.raises(RuntimeError) as e:
 
-            @agent.register_for_llm(description="run cell in ipython and return the execution result.")
-            def exec_python(cell: Annotated[str, "Valid Python cell to execute."]) -> str:
-                pass
+def test_register_for_llm_without_configuration():
+    try:
+        ConversableAgent(name="agent", llm_config={"config_list": []})
+        assert False, "Expected ConversableAgent to throw ValueError."
+    except ValueError as e:
+        assert e.args[0] == "Please specify at least one configuration in 'llm_config'."
+
 
-        assert e.value.args[0] == "LLM config must be setup before registering a function for LLM."
+def test_register_for_llm_without_model_name():
+    try:
+        ConversableAgent(name="agent", llm_config={"config_list": [{"model": "", "api_key": ""}]})
+        assert False, "Expected ConversableAgent to throw ValueError."
+    except ValueError as e:
+        assert e.args[0] == "Please specify a value for the 'model' in 'llm_config'."
 
 
 def test_register_for_execution():
     with pytest.MonkeyPatch.context() as mp:
         mp.setenv("OPENAI_API_KEY", MOCK_OPEN_AI_API_KEY)
-        agent = ConversableAgent(name="agent", llm_config={"config_list": []})
+        agent = ConversableAgent(name="agent", llm_config={"config_list": [{"model": "gpt-4", "api_key": ""}]})
         user_proxy_1 = UserProxyAgent(name="user_proxy_1")
         user_proxy_2 = UserProxyAgent(name="user_proxy_2")
 
@@ -827,7 +835,7 @@ async def exec_sh(script: Annotated[str, "Valid shell script to execute."]):
 def test_register_functions():
     with pytest.MonkeyPatch.context() as mp:
         mp.setenv("OPENAI_API_KEY", MOCK_OPEN_AI_API_KEY)
-        agent = ConversableAgent(name="agent", llm_config={"config_list": []})
+        agent = ConversableAgent(name="agent", llm_config={"config_list": [{"model": "gpt-4", "api_key": ""}]})
         user_proxy = UserProxyAgent(name="user_proxy")
 
         def exec_python(cell: Annotated[str, "Valid Python cell to execute."]) -> str: