diff --git a/dotnet/src/Connectors/Connectors.Google.UnitTests/Core/Gemini/Clients/GeminiChatClientFunctionCallingTests.cs b/dotnet/src/Connectors/Connectors.Google.UnitTests/Core/Gemini/Clients/GeminiChatClientFunctionCallingTests.cs
new file mode 100644
index 000000000000..49b96537bdf3
--- /dev/null
+++ b/dotnet/src/Connectors/Connectors.Google.UnitTests/Core/Gemini/Clients/GeminiChatClientFunctionCallingTests.cs
@@ -0,0 +1,178 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+using System;
+using System.Collections.Generic;
+using System.Globalization;
+using System.IO;
+using System.Linq;
+using System.Net.Http;
+using System.Text.Json;
+using System.Threading.Tasks;
+using Microsoft.Extensions.AI;
+using Microsoft.SemanticKernel;
+using Microsoft.SemanticKernel.ChatCompletion;
+using Microsoft.SemanticKernel.Connectors.Google;
+using Microsoft.SemanticKernel.Connectors.Google.Core;
+using Xunit;
+
+namespace SemanticKernel.Connectors.Google.UnitTests.Core.Gemini.Clients;
+
+/// <summary>
+/// Unit tests for IChatClient-based function calling with Gemini using FunctionChoiceBehavior.
+/// </summary>
+public sealed class GeminiChatClientFunctionCallingTests : IDisposable
+{
+    private readonly HttpClient _httpClient;
+    private readonly string _responseContent;
+    private readonly string _responseContentWithFunction;
+    private readonly HttpMessageHandlerStub _messageHandlerStub;
+    private readonly GeminiFunction _timePluginDate, _timePluginNow;
+    private readonly Kernel _kernelWithFunctions;
+    private const string ChatTestDataFilePath = "./TestData/chat_one_response.json";
+    private const string ChatTestDataWithFunctionFilePath = "./TestData/chat_one_function_response.json";
+
+    public GeminiChatClientFunctionCallingTests()
+    {
+        this._responseContent = File.ReadAllText(ChatTestDataFilePath);
+        this._responseContentWithFunction = File.ReadAllText(ChatTestDataWithFunctionFilePath)
+            .Replace("%nameSeparator%", GeminiFunction.NameSeparator, StringComparison.Ordinal);
+        this._messageHandlerStub = new HttpMessageHandlerStub();
+        this._messageHandlerStub.ResponseToReturn.Content = new StringContent(
+            this._responseContent);
+
+        this._httpClient = new HttpClient(this._messageHandlerStub, false);
+
+        var kernelPlugin = KernelPluginFactory.CreateFromFunctions("TimePlugin", new[]
+        {
+            KernelFunctionFactory.CreateFromMethod((string? format = null)
+                => DateTime.Now.Date.ToString(format, CultureInfo.InvariantCulture), "Date", "TimePlugin.Date"),
+            KernelFunctionFactory.CreateFromMethod(()
+                    => DateTime.Now.ToString("", CultureInfo.InvariantCulture), "Now", "TimePlugin.Now",
+                parameters: [new KernelParameterMetadata("param1") { ParameterType = typeof(string), Description = "desc", IsRequired = false }]),
+        });
+        IList<KernelFunctionMetadata> functions = kernelPlugin.GetFunctionsMetadata();
+
+        this._timePluginDate = functions[0].ToGeminiFunction();
+        this._timePluginNow = functions[1].ToGeminiFunction();
+
+        this._kernelWithFunctions = new Kernel();
+        this._kernelWithFunctions.Plugins.Add(kernelPlugin);
+    }
+
+    [Fact]
+    public async Task ChatClientShouldConvertToIChatClientSuccessfullyAsync()
+    {
+        // Arrange
+        var chatCompletionService = this.CreateChatCompletionService();
+
+        // Act
+        var chatClient = chatCompletionService.AsChatClient();
+
+        // Assert - Verify conversion works
+        Assert.NotNull(chatClient);
+        Assert.IsAssignableFrom<IChatClient>(chatClient);
+
+        // Verify we can make a basic call through IChatClient
+        var messages = new List<ChatMessage>
+        {
+            new(ChatRole.User, "What time is it?")
+        };
+
+        var response = await chatClient.GetResponseAsync(messages);
+
+        Assert.NotNull(response);
+        Assert.NotEmpty(response.Messages);
+    }
+
+    [Fact]
+    public async Task ChatClientShouldReceiveFunctionCallsInResponseAsync()
+    {
+        // Arrange
+        this._messageHandlerStub.ResponseToReturn.Content = new StringContent(this._responseContentWithFunction);
+        var chatCompletionService = this.CreateChatCompletionService();
+        var chatClient = chatCompletionService.AsChatClient();
+
+        var settings = new GeminiPromptExecutionSettings
+        {
+            FunctionChoiceBehavior = FunctionChoiceBehavior.Auto(autoInvoke: false)
+        };
+        var chatOptions = settings.ToChatOptions(this._kernelWithFunctions);
+
+        var messages = new List<ChatMessage>
+        {
+            new(ChatRole.User, "What time is it?")
+        };
+
+        // Act
+        var response = await chatClient.GetResponseAsync(messages, chatOptions);
+
+        // Assert - Verify that FunctionCallContent is returned in the response
+        Assert.NotNull(response);
+        var functionCalls = response.Messages
+            .SelectMany(m => m.Contents)
+            .OfType<Microsoft.Extensions.AI.FunctionCallContent>()
+            .ToList();
+
+        Assert.NotEmpty(functionCalls);
+        var functionCall = functionCalls.First();
+        Assert.Contains(this._timePluginNow.FunctionName, functionCall.Name, StringComparison.OrdinalIgnoreCase);
+    }
+
+    [Fact]
+    public async Task ChatClientShouldStreamResponsesAsync()
+    {
+        // Arrange
+        var chatCompletionService = this.CreateChatCompletionService();
+        var chatClient = chatCompletionService.AsChatClient();
+
+        var settings = new GeminiPromptExecutionSettings
+        {
+            FunctionChoiceBehavior = FunctionChoiceBehavior.Auto()
+        };
+        var chatOptions = settings.ToChatOptions(this._kernelWithFunctions);
+
+        var messages = new List<ChatMessage>
+        {
+            new(ChatRole.User, "What time is it?")
+        };
+
+        // Act
+        var updates = new List<ChatResponseUpdate>();
+        await foreach (var update in chatClient.GetStreamingResponseAsync(messages, chatOptions))
+        {
+            updates.Add(update);
+        }
+
+        // Assert - Verify that streaming works and returns updates
+        Assert.NotEmpty(updates);
+    }
+
+    [Fact]
+    public async Task AsChatClientConvertsServiceToIChatClientAsync()
+    {
+        // Arrange
+        var chatCompletionService = this.CreateChatCompletionService();
+
+        // Act
+        var chatClient = chatCompletionService.AsChatClient();
+
+        // Assert
+        Assert.NotNull(chatClient);
+        Assert.IsAssignableFrom<IChatClient>(chatClient);
+    }
+
+    private GoogleAIGeminiChatCompletionService CreateChatCompletionService(HttpClient? httpClient = null)
+    {
+        return new GoogleAIGeminiChatCompletionService(
+            modelId: "fake-model",
+            apiKey: "fake-key",
+            apiVersion: GoogleAIVersion.V1,
+            httpClient: httpClient ?? this._httpClient);
+    }
+
+    public void Dispose()
+    {
+        this._httpClient.Dispose();
+        this._messageHandlerStub.Dispose();
+    }
+}
diff --git a/dotnet/src/Connectors/Connectors.Google.UnitTests/GeminiToolCallBehaviorTests.cs b/dotnet/src/Connectors/Connectors.Google.UnitTests/GeminiToolCallBehaviorTests.cs
index 958f2ad27082..4833fac1a4cd 100644
--- a/dotnet/src/Connectors/Connectors.Google.UnitTests/GeminiToolCallBehaviorTests.cs
+++ b/dotnet/src/Connectors/Connectors.Google.UnitTests/GeminiToolCallBehaviorTests.cs
@@ -194,6 +194,111 @@ public void KernelFunctionsCloneReturnsCorrectClone()
         Assert.Equivalent(toolcallbehavior, clone, strict: true);
     }
 
+    [Fact]
+    public void FunctionChoiceBehaviorAutoConvertsToAutoInvokeKernelFunctions()
+    {
+        // Arrange
+        var settings = new GeminiPromptExecutionSettings
+        {
+            FunctionChoiceBehavior = FunctionChoiceBehavior.Auto()
+        };
+
+        // Act
+        var converted = GeminiPromptExecutionSettings.FromExecutionSettings(settings);
+
+        // Assert
+        Assert.NotNull(converted.ToolCallBehavior);
+        Assert.IsType<GeminiToolCallBehavior.KernelFunctions>(converted.ToolCallBehavior);
+        Assert.True(converted.ToolCallBehavior.MaximumAutoInvokeAttempts > 0);
+    }
+
+    [Fact]
+    public void FunctionChoiceBehaviorAutoWithNoAutoInvokeConvertsToEnableKernelFunctions()
+    {
+        // Arrange
+        var settings = new GeminiPromptExecutionSettings
+        {
+            FunctionChoiceBehavior = FunctionChoiceBehavior.Auto(autoInvoke: false)
+        };
+
+        // Act
+        var converted = GeminiPromptExecutionSettings.FromExecutionSettings(settings);
+
+        // Assert
+        Assert.NotNull(converted.ToolCallBehavior);
+        Assert.IsType<GeminiToolCallBehavior.KernelFunctions>(converted.ToolCallBehavior);
+        Assert.Equal(0, converted.ToolCallBehavior.MaximumAutoInvokeAttempts);
+    }
+
+    [Fact]
+    public void FunctionChoiceBehaviorRequiredConvertsToAutoInvokeKernelFunctions()
+    {
+        // Arrange
+        var settings = new GeminiPromptExecutionSettings
+        {
+            FunctionChoiceBehavior = FunctionChoiceBehavior.Required()
+        };
+
+        // Act
+        var converted = GeminiPromptExecutionSettings.FromExecutionSettings(settings);
+
+        // Assert
+        Assert.NotNull(converted.ToolCallBehavior);
+        Assert.IsType<GeminiToolCallBehavior.KernelFunctions>(converted.ToolCallBehavior);
+        Assert.True(converted.ToolCallBehavior.MaximumAutoInvokeAttempts > 0);
+    }
+
+    [Fact]
+    public void FunctionChoiceBehaviorNoneConvertsToEnableKernelFunctions()
+    {
+        // Arrange
+        var settings = new GeminiPromptExecutionSettings
+        {
+            FunctionChoiceBehavior = FunctionChoiceBehavior.None()
+        };
+
+        // Act
+        var converted = GeminiPromptExecutionSettings.FromExecutionSettings(settings);
+
+        // Assert
+        Assert.NotNull(converted.ToolCallBehavior);
+        Assert.IsType<GeminiToolCallBehavior.KernelFunctions>(converted.ToolCallBehavior);
+        // None behavior doesn't auto-invoke
+        Assert.Equal(0, converted.ToolCallBehavior.MaximumAutoInvokeAttempts);
+    }
+
+    [Fact]
+    public void GeminiPromptExecutionSettingsWithNoFunctionChoiceBehaviorDoesNotSetToolCallBehavior()
+    {
+        // Arrange
+        var settings = new GeminiPromptExecutionSettings();
+
+        // Act
+        var converted = GeminiPromptExecutionSettings.FromExecutionSettings(settings);
+
+        // Assert
+        Assert.Null(converted.ToolCallBehavior);
+    }
+
+    [Fact]
+    public void GeminiPromptExecutionSettingsPreservesExistingToolCallBehavior()
+    {
+        // Arrange
+        var settings = new GeminiPromptExecutionSettings
+        {
+            ToolCallBehavior = GeminiToolCallBehavior.EnableKernelFunctions,
+            FunctionChoiceBehavior = FunctionChoiceBehavior.Auto()
+        };
+
+        // Act
+        var converted = GeminiPromptExecutionSettings.FromExecutionSettings(settings);
+
+        // Assert - ToolCallBehavior should be preserved when already set
+        Assert.NotNull(converted.ToolCallBehavior);
+        Assert.IsType<GeminiToolCallBehavior.KernelFunctions>(converted.ToolCallBehavior);
+        Assert.Equal(0, converted.ToolCallBehavior.MaximumAutoInvokeAttempts);
+    }
+
     private static KernelPlugin GetTestPlugin()
     {
         var function = KernelFunctionFactory.CreateFromMethod(
diff --git a/dotnet/src/Connectors/Connectors.Google/GeminiPromptExecutionSettings.cs b/dotnet/src/Connectors/Connectors.Google/GeminiPromptExecutionSettings.cs
index 5f8bc0874cc2..a9729f518899 100644
--- a/dotnet/src/Connectors/Connectors.Google/GeminiPromptExecutionSettings.cs
+++ b/dotnet/src/Connectors/Connectors.Google/GeminiPromptExecutionSettings.cs
@@ -188,6 +188,9 @@ public IDictionary<string, string>? Labels
     /// the function, and sending back the result. The intermediate messages will be retained in the
     /// <see cref="ChatHistory"/> if an instance was provided.
     /// </remarks>
+    /// <remarks>
+    /// This property is deprecated. Use <see cref="PromptExecutionSettings.FunctionChoiceBehavior"/> instead.
+    /// </remarks>
     public GeminiToolCallBehavior? ToolCallBehavior
     {
         get => this._toolCallBehavior;
@@ -357,11 +360,71 @@ public static GeminiPromptExecutionSettings FromExecutionSettings(PromptExecutio
         {
             case null:
                 return new GeminiPromptExecutionSettings();
-            case GeminiPromptExecutionSettings settings:
-                return settings;
+            case GeminiPromptExecutionSettings geminiSettings:
+                // If FunctionChoiceBehavior is set and ToolCallBehavior is not, convert it
+                if (geminiSettings.FunctionChoiceBehavior is not null && geminiSettings.ToolCallBehavior is null)
+                {
+                    geminiSettings.ToolCallBehavior = ConvertFunctionChoiceBehaviorToToolCallBehavior(geminiSettings.FunctionChoiceBehavior);
+                }
+                return geminiSettings;
         }
 
         var json = JsonSerializer.Serialize(executionSettings);
-        return JsonSerializer.Deserialize<GeminiPromptExecutionSettings>(json, JsonOptionsCache.ReadPermissive)!;
+        var settings = JsonSerializer.Deserialize<GeminiPromptExecutionSettings>(json, JsonOptionsCache.ReadPermissive)!;
+
+        // If FunctionChoiceBehavior is set and ToolCallBehavior is not, convert it
+        if (executionSettings.FunctionChoiceBehavior is not null && settings.ToolCallBehavior is null)
+        {
+            settings.ToolCallBehavior = ConvertFunctionChoiceBehaviorToToolCallBehavior(executionSettings.FunctionChoiceBehavior);
+        }
+
+        return settings;
+    }
+
+    /// <summary>
+    /// Shared empty kernel instance used for FunctionChoiceBehavior conversion.
+    /// </summary>
+    private static readonly Kernel s_emptyKernel = new();
+
+    /// <summary>
+    /// Converts a <see cref="FunctionChoiceBehavior"/> to a <see cref="GeminiToolCallBehavior"/>.
+    /// </summary>
+    /// <param name="functionChoiceBehavior">The <see cref="FunctionChoiceBehavior"/> to convert.</param>
+    /// <returns>The converted <see cref="GeminiToolCallBehavior"/>.</returns>
+    internal static GeminiToolCallBehavior? ConvertFunctionChoiceBehaviorToToolCallBehavior(FunctionChoiceBehavior? functionChoiceBehavior)
+    {
+        if (functionChoiceBehavior is null)
+        {
+            return null;
+        }
+
+        // Check the type and determine auto-invoke by reflection or known behavior types
+        // All FunctionChoiceBehavior types (Auto, Required, None) support auto-invoke
+        // We use a simple approach: get the configuration with minimal context to check AutoInvoke
+        try
+        {
+            var context = new FunctionChoiceBehaviorConfigurationContext(new ChatHistory())
+            {
+                Kernel = s_emptyKernel, // Provide an empty kernel for the configuration
+                RequestSequenceIndex = 0
+            };
+            var config = functionChoiceBehavior.GetConfiguration(context);
+
+            // Return appropriate GeminiToolCallBehavior based on AutoInvoke setting
+            if (config.AutoInvoke)
+            {
+                return GeminiToolCallBehavior.AutoInvokeKernelFunctions;
+            }
+
+            return GeminiToolCallBehavior.EnableKernelFunctions;
+        }
+#pragma warning disable CA1031 // Do not catch general exception types
+        catch
+#pragma warning restore CA1031
+        {
+            // If we can't get configuration (e.g., due to missing dependencies or unexpected state),
+            // default to EnableKernelFunctions as the safer option that doesn't auto-invoke
+            return GeminiToolCallBehavior.EnableKernelFunctions;
+        }
     }
 }
diff --git a/dotnet/src/Connectors/Connectors.Google/Models/Gemini/GeminiChatMessageContent.cs b/dotnet/src/Connectors/Connectors.Google/Models/Gemini/GeminiChatMessageContent.cs
index ac5f6ced3e8b..6154decf12d8 100644
--- a/dotnet/src/Connectors/Connectors.Google/Models/Gemini/GeminiChatMessageContent.cs
+++ b/dotnet/src/Connectors/Connectors.Google/Models/Gemini/GeminiChatMessageContent.cs
@@ -1,5 +1,6 @@
 // Copyright (c) Microsoft. All rights reserved.
 
+using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
@@ -38,6 +39,16 @@ public GeminiChatMessageContent(GeminiFunctionToolResult calledToolResult)
         Verify.NotNull(calledToolResult);
 
         this.CalledToolResult = calledToolResult;
+
+        // Parse plugin and function names from FullyQualifiedName
+        var (pluginName, functionName) = ParseFullyQualifiedName(calledToolResult.FullyQualifiedName);
+
+        // Also populate Items collection with FunctionResultContent for compatibility with FunctionChoiceBehavior
+        this.Items.Add(new FunctionResultContent(
+            functionName: functionName,
+            pluginName: pluginName,
+            callId: null, // Gemini doesn't provide call IDs
+            result: calledToolResult.FunctionResult));
     }
 
     /// <summary>
@@ -63,6 +74,35 @@ internal GeminiChatMessageContent(
             metadata: metadata)
     {
         this.CalledToolResult = calledToolResult;
+
+        // Also populate Items collection with FunctionResultContent for compatibility with FunctionChoiceBehavior
+        if (calledToolResult is not null)
+        {
+            // Parse plugin and function names from FullyQualifiedName
+            var (pluginName, functionName) = ParseFullyQualifiedName(calledToolResult.FullyQualifiedName);
+
+            this.Items.Add(new FunctionResultContent(
+                functionName: functionName,
+                pluginName: pluginName,
+                callId: null, // Gemini doesn't provide call IDs
+                result: calledToolResult.FunctionResult));
+        }
+    }
+
+    /// <summary>
+    /// Parses a fully qualified function name into plugin name and function name.
+    /// </summary>
+    private static (string? PluginName, string FunctionName) ParseFullyQualifiedName(string fullyQualifiedName)
+    {
+        int separatorPos = fullyQualifiedName.IndexOf(GeminiFunction.NameSeparator, StringComparison.Ordinal);
+        if (separatorPos >= 0)
+        {
+            string pluginName = fullyQualifiedName.Substring(0, separatorPos).Trim();
+            string functionName = fullyQualifiedName.Substring(separatorPos + GeminiFunction.NameSeparator.Length).Trim();
+            return (pluginName, functionName);
+        }
+
+        return (null, fullyQualifiedName);
     }
 
     /// <summary>
@@ -88,6 +128,29 @@ internal GeminiChatMessageContent(
             metadata: metadata)
     {
         this.ToolCalls = functionsToolCalls?.Select(tool => new GeminiFunctionToolCall(tool)).ToList();
+
+        // Also populate Items collection with FunctionCallContent for compatibility with FunctionChoiceBehavior
+        if (this.ToolCalls is not null)
+        {
+            foreach (var toolCall in this.ToolCalls)
+            {
+                KernelArguments? arguments = null;
+                if (toolCall.Arguments is not null)
+                {
+                    arguments = new KernelArguments();
+                    foreach (var arg in toolCall.Arguments)
+                    {
+                        arguments[arg.Key] = arg.Value;
+                    }
+                }
+
+                this.Items.Add(new FunctionCallContent(
+                    functionName: toolCall.FunctionName,
+                    pluginName: toolCall.PluginName,
+                    id: null, // Gemini doesn't provide call IDs
+                    arguments: arguments));
+            }
+        }
     }
 
     /// <summary>