diff --git a/dotnet/src/Connectors/Connectors.OpenAI.UnitTests/Services/OpenAIChatCompletionServiceTests.cs b/dotnet/src/Connectors/Connectors.OpenAI.UnitTests/Services/OpenAIChatCompletionServiceTests.cs
index 397c9bb0e39d..385880b21322 100644
--- a/dotnet/src/Connectors/Connectors.OpenAI.UnitTests/Services/OpenAIChatCompletionServiceTests.cs
+++ b/dotnet/src/Connectors/Connectors.OpenAI.UnitTests/Services/OpenAIChatCompletionServiceTests.cs
@@ -916,6 +916,34 @@ public async Task FunctionResultsCanBeProvidedToLLMAsOneResultPerChatMessageAsyn
         Assert.Equal("2", assistantMessage2.GetProperty("tool_call_id").GetString());
     }
 
+    [Fact]
+    public async Task FunctionResultsWithoutCallIdThrowsClearExceptionAsync()
+    {
+        // Arrange
+        this._messageHandlerStub.ResponseToReturn = new HttpResponseMessage(System.Net.HttpStatusCode.OK)
+        {
+            Content = new StringContent(ChatCompletionResponse)
+        };
+
+        var sut = new OpenAIChatCompletionService(modelId: "gpt-3.5-turbo", apiKey: "NOKEY", httpClient: this._httpClient);
+
+        var chatHistory = new ChatHistory
+        {
+            new ChatMessageContent(AuthorRole.Tool,
+            [
+                new FunctionResultContent(functionName: "GetCurrentWeather", pluginName: "MyPlugin", callId: null, result: "rainy")
+            ])
+        };
+
+        var settings = new OpenAIPromptExecutionSettings() { ToolCallBehavior = ToolCallBehavior.EnableKernelFunctions };
+
+        // Act
+        var exception = await Assert.ThrowsAsync<ArgumentException>(() => sut.GetChatMessageContentAsync(chatHistory, settings));
+
+        // Assert
+        Assert.Contains("missing a tool call id", exception.Message, StringComparison.OrdinalIgnoreCase);
+    }
+
     [Fact]
     public async Task FunctionResultsCanBeProvidedToLLMAsManyResultsInOneChatMessageAsync()
     {
diff --git a/dotnet/src/Connectors/Connectors.OpenAI/Core/ClientCore.ChatCompletion.cs b/dotnet/src/Connectors/Connectors.OpenAI/Core/ClientCore.ChatCompletion.cs
index 7f8dfa41a2d9..87fa8932e1c6 100644
--- a/dotnet/src/Connectors/Connectors.OpenAI/Core/ClientCore.ChatCompletion.cs
+++ b/dotnet/src/Connectors/Connectors.OpenAI/Core/ClientCore.ChatCompletion.cs
@@ -759,6 +759,13 @@ private static List<ChatMessage> CreateRequestMessages(ChatMessageContent messag
                     continue;
                 }
 
+                if (string.IsNullOrWhiteSpace(resultContent.CallId))
+                {
+                    throw new ArgumentException(
+                        $"Function result message is missing a tool call ID. Provide {nameof(FunctionResultContent.CallId)} when sending tool results to OpenAI.",
+                        nameof(message));
+                }
+
                 toolMessages ??= [];
 
                 if (resultContent.Result is Exception ex)