diff --git a/Directory.Packages.props b/Directory.Packages.props
index 1397c7567..6e0da532b 100644
--- a/Directory.Packages.props
+++ b/Directory.Packages.props
@@ -35,6 +35,7 @@
     <PackageVersion Include="Newtonsoft.Json" Version="13.0.1" />
     <PackageVersion Include="PolySharp" Version="1.13.2" />
     <PackageVersion Include="StackExchange.Redis" Version="2.0.601" />
+    <PackageVersion Include="System.Text.Json" Version="9.0.0" />
     <PackageVersion Include="Microsoft.CodeAnalysis.PublicApiAnalyzers" Version="3.3.4" />
   </ItemGroup>
   <!-- for tests -->
diff --git a/src/MagicOnion.Server.JsonTranscoding/MagicOnionJsonTranscodingGrpcMethodBinder.cs b/src/MagicOnion.Server.JsonTranscoding/MagicOnionJsonTranscodingGrpcMethodBinder.cs
index 7f54a5df2..910942702 100644
--- a/src/MagicOnion.Server.JsonTranscoding/MagicOnionJsonTranscodingGrpcMethodBinder.cs
+++ b/src/MagicOnion.Server.JsonTranscoding/MagicOnionJsonTranscodingGrpcMethodBinder.cs
@@ -44,7 +44,11 @@ public void BindUnary<TRequest, TResponse, TRawRequest, TRawResponse>(IMagicOnio
                 var memStream = new MemoryStream();
                 await context.Request.BodyReader.CopyToAsync(memStream);
 
-                var request = grpcMethod.RequestMarshaller.ContextualDeserializer(new DeserializationContextImpl(memStream.ToArray()));
+                // If the request type is `Nil` (parameter-less method), we always ignore the request body.
+                TRawRequest request = (typeof(TRequest) == typeof(Nil))
+                    ? (TRawRequest)(object)Box.Create(Nil.Default)
+                    : grpcMethod.RequestMarshaller.ContextualDeserializer(new DeserializationContextImpl(memStream.ToArray()));
+
                 var response = await unaryMethodHandler(handle.Instance, request, serverCallContext);
 
                 context.Response.ContentType = "application/json";
diff --git a/tests/MagicOnion.Server.InternalTesting/MagicOnionApplicationFactory.cs b/tests/MagicOnion.Server.InternalTesting/MagicOnionApplicationFactory.cs
index 22c7ebddb..14f6600c7 100644
--- a/tests/MagicOnion.Server.InternalTesting/MagicOnionApplicationFactory.cs
+++ b/tests/MagicOnion.Server.InternalTesting/MagicOnionApplicationFactory.cs
@@ -35,7 +35,7 @@ protected override void ConfigureWebHost(IWebHostBuilder builder)
         builder.ConfigureServices(services =>
         {
             services.AddKeyedSingleton<ConcurrentDictionary<string, object>>(ItemsKey);
-            services.AddMagicOnion();
+            OnConfigureMagicOnionBuilder(services.AddMagicOnion());
         });
         builder.Configure(app =>
         {
@@ -47,6 +47,8 @@ protected override void ConfigureWebHost(IWebHostBuilder builder)
         });
     }
 
+    protected virtual void OnConfigureMagicOnionBuilder(IMagicOnionServerBuilder builder){}
+
     protected abstract IEnumerable<Type> GetServiceImplementationTypes();
 
     public WebApplicationFactory<Program> WithMagicOnionOptions(Action<MagicOnionOptions> configure)
diff --git a/tests/MagicOnion.Server.JsonTranscoding.Tests/JsonTranscodingEnabledMagicOnionApplicationFactory.cs b/tests/MagicOnion.Server.JsonTranscoding.Tests/JsonTranscodingEnabledMagicOnionApplicationFactory.cs
new file mode 100644
index 000000000..a742d6f67
--- /dev/null
+++ b/tests/MagicOnion.Server.JsonTranscoding.Tests/JsonTranscodingEnabledMagicOnionApplicationFactory.cs
@@ -0,0 +1,11 @@
+using Microsoft.Extensions.DependencyInjection;
+
+namespace MagicOnion.Server.JsonTranscoding.Tests;
+
+public class JsonTranscodingEnabledMagicOnionApplicationFactory<T> : MagicOnionApplicationFactory<T>
+{
+    protected override void OnConfigureMagicOnionBuilder(IMagicOnionServerBuilder builder)
+    {
+        builder.AddJsonTranscoding();
+    }
+}
diff --git a/tests/MagicOnion.Server.JsonTranscoding.Tests/MagicOnion.Server.JsonTranscoding.Tests.csproj b/tests/MagicOnion.Server.JsonTranscoding.Tests/MagicOnion.Server.JsonTranscoding.Tests.csproj
index a2b37b466..d0d2b65e9 100644
--- a/tests/MagicOnion.Server.JsonTranscoding.Tests/MagicOnion.Server.JsonTranscoding.Tests.csproj
+++ b/tests/MagicOnion.Server.JsonTranscoding.Tests/MagicOnion.Server.JsonTranscoding.Tests.csproj
@@ -12,10 +12,16 @@
   <ItemGroup>
     <PackageReference Include="coverlet.collector" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" />
+    <PackageReference Include="System.Text.Json" />
     <PackageReference Include="xunit" />
     <PackageReference Include="xunit.runner.visualstudio" />
   </ItemGroup>
 
+  <ItemGroup>
+    <ProjectReference Include="..\..\src\MagicOnion.Server.JsonTranscoding\MagicOnion.Server.JsonTranscoding.csproj" />
+    <ProjectReference Include="..\MagicOnion.Server.InternalTesting\MagicOnion.Server.InternalTesting.csproj" />
+  </ItemGroup>
+
   <ItemGroup>
     <Using Include="Xunit" />
   </ItemGroup>
diff --git a/tests/MagicOnion.Server.JsonTranscoding.Tests/UnaryFunctionalTests.cs b/tests/MagicOnion.Server.JsonTranscoding.Tests/UnaryFunctionalTests.cs
new file mode 100644
index 000000000..c60214a96
--- /dev/null
+++ b/tests/MagicOnion.Server.JsonTranscoding.Tests/UnaryFunctionalTests.cs
@@ -0,0 +1,130 @@
+using System.Collections.Concurrent;
+using System.Net;
+using System.Net.Http.Headers;
+using System.Text.Json;
+using MessagePack;
+using Microsoft.Extensions.DependencyInjection;
+
+namespace MagicOnion.Server.JsonTranscoding.Tests;
+
+public class UnaryFunctionalTests(JsonTranscodingEnabledMagicOnionApplicationFactory<TestService> factory) : IClassFixture<JsonTranscodingEnabledMagicOnionApplicationFactory<TestService>>
+{
+    [Fact]
+    public async Task NotImplemented()
+    {
+        // Arrange
+        var httpClient = factory.CreateDefaultClient();
+
+        // Act
+        var response = await httpClient.PostAsync($"http://localhost/_/ITestService/NotImplemented", new StringContent(string.Empty, new MediaTypeHeaderValue("application/json")));
+
+        // Assert
+        Assert.Equal(HttpStatusCode.NotFound, response.StatusCode);
+    }
+
+    [Fact]
+    public async Task Method_NoParameter_NoResult()
+    {
+        // Arrange
+        var httpClient = factory.CreateDefaultClient();
+
+        // Act
+        var response = await httpClient.PostAsync($"http://localhost/_/ITestService/Method_NoParameter_NoResult", new StringContent(string.Empty, new MediaTypeHeaderValue("application/json")));
+        var content = await response.Content.ReadAsStringAsync();
+
+        // Assert
+        var result = default(object); // null
+        Assert.Equal(HttpStatusCode.OK, response.StatusCode);
+        Assert.Equal(result, JsonSerializer.Deserialize<object>(content));
+        Assert.Equal("application/json", response.Content.Headers.ContentType?.ToString());
+        Assert.True((bool)factory.Items.GetValueOrDefault($"{nameof(Method_NoParameter_NoResult)}.Called", false));
+    }
+
+    [Fact]
+    public async Task Method_NoParameter_ResultRefType()
+    {
+        // Arrange
+        var httpClient = factory.CreateDefaultClient();
+
+        // Act
+        var response = await httpClient.PostAsync($"http://localhost/_/ITestService/Method_NoParameter_ResultRefType", new StringContent(string.Empty, new MediaTypeHeaderValue("application/json")));
+        var content = await response.Content.ReadAsStringAsync();
+
+        // Assert
+        var result = nameof(Method_NoParameter_ResultRefType); // string
+        Assert.Equal(HttpStatusCode.OK, response.StatusCode);
+        Assert.Equal(result, JsonSerializer.Deserialize<string>(content));
+        Assert.Equal("application/json", response.Content.Headers.ContentType?.ToString());
+    }
+
+    [Fact]
+    public async Task Method_NoParameter_ResultComplexType()
+    {
+        // Arrange
+        var httpClient = factory.CreateDefaultClient();
+
+        // Act
+        var response = await httpClient.PostAsync($"http://localhost/_/ITestService/Method_NoParameter_ResultComplexType", new StringContent(string.Empty, new MediaTypeHeaderValue("application/json")));
+        var content = await response.Content.ReadAsStringAsync();
+
+        // Assert
+        object[] result = [1234, "Alice", true, new object[] { 98765432100, "Hello!" }];
+        Assert.Equal(HttpStatusCode.OK, response.StatusCode);
+        Assert.Equal(JsonSerializer.Serialize(result), JsonSerializer.Serialize(JsonSerializer.Deserialize<object>(content)));
+        Assert.Equal("application/json", response.Content.Headers.ContentType?.ToString());
+    }
+}
+
+public interface ITestService : IService<ITestService>
+{
+    UnaryResult Method_NoParameter_NoResult();
+    UnaryResult<string> Method_NoParameter_ResultRefType();
+    UnaryResult<TestResponse> Method_NoParameter_ResultComplexType();
+}
+
+[MessagePackObject]
+public class TestResponse
+{
+    [Key(0)]
+    public int A { get; set; }
+    [Key(1)]
+    public required string B { get; init; }
+    [Key(2)]
+    public bool C { get; set; }
+    [Key(3)]
+    public required InnerResponse Inner { get; init; }
+
+    [MessagePackObject]
+    public class InnerResponse
+    {
+        [Key(0)]
+        public long D { get; set; }
+        [Key(1)]
+        public required string E { get; init; }
+    }
+}
+
+public class TestService([FromKeyedServices(MagicOnionApplicationFactory.ItemsKey)] ConcurrentDictionary<string, object> items) : ServiceBase<ITestService>, ITestService
+{
+    public UnaryResult Method_NoParameter_NoResult()
+    {
+        items[$"{nameof(Method_NoParameter_NoResult)}.Called"] = true;
+        return default;
+    }
+
+public UnaryResult<string> Method_NoParameter_ResultRefType()
+        => UnaryResult.FromResult(nameof(Method_NoParameter_ResultRefType));
+
+    public UnaryResult<TestResponse> Method_NoParameter_ResultComplexType()
+        => UnaryResult.FromResult(new TestResponse()
+        {
+            A = 1234,
+            B = "Alice",
+            C = true,
+            Inner = new TestResponse.InnerResponse()
+            {
+                D = 98765432100,
+                E = "Hello!",
+            },
+        });
+}
diff --git a/tests/MagicOnion.Server.JsonTranscoding.Tests/Usings.cs b/tests/MagicOnion.Server.JsonTranscoding.Tests/Usings.cs
new file mode 100644
index 000000000..e6bc4f2db
--- /dev/null
+++ b/tests/MagicOnion.Server.JsonTranscoding.Tests/Usings.cs
@@ -0,0 +1,2 @@
+global using Xunit;
+global using MagicOnion.Server.InternalTesting;