diff --git a/modules/openapi-generator/src/main/resources/csharp/libraries/generichost/JsonConverter.mustache b/modules/openapi-generator/src/main/resources/csharp/libraries/generichost/JsonConverter.mustache
index 7948f79dbf7c..cff653bf3c39 100644
--- a/modules/openapi-generator/src/main/resources/csharp/libraries/generichost/JsonConverter.mustache
+++ b/modules/openapi-generator/src/main/resources/csharp/libraries/generichost/JsonConverter.mustache
@@ -376,7 +376,41 @@
 
             {{/children}}
             {{/discriminator}}
+            {{^model.discriminator}}
+            {{#composedSchemas}}
+            {{#oneOf}}
+            {{^vendorExtensions.x-duplicated-data-type}}
+            {{#isPrimitiveType}}
+            if ({{#lambda.camelcase_sanitize_param}}{{classname}}{{/lambda.camelcase_sanitize_param}}.{{name}} != null)
+            {
+                JsonSerializer.Serialize(writer, {{#lambda.camelcase_sanitize_param}}{{classname}}{{/lambda.camelcase_sanitize_param}}.{{name}}, jsonSerializerOptions);
+                return;
+            }
+
+            {{/isPrimitiveType}}
+            {{/vendorExtensions.x-duplicated-data-type}}
+            {{/oneOf}}
+            {{/composedSchemas}}
+            {{/model.discriminator}}
             writer.WriteStartObject();
+            {{^model.discriminator}}
+            {{#composedSchemas}}
+            {{#oneOf}}
+            {{^vendorExtensions.x-duplicated-data-type}}
+            {{#isModel}}
+            {{^isContainer}}
+            if ({{#lambda.camelcase_sanitize_param}}{{classname}}{{/lambda.camelcase_sanitize_param}}.{{name}} != null)
+            {
+                {{baseType}}JsonConverter {{#lambda.camelcase_sanitize_param}}{{baseType}}JsonConverter{{/lambda.camelcase_sanitize_param}} = new {{baseType}}JsonConverter();
+                {{#lambda.camelcase_sanitize_param}}{{baseType}}JsonConverter{{/lambda.camelcase_sanitize_param}}.WriteProperties(writer, {{#lambda.camelcase_sanitize_param}}{{classname}}{{/lambda.camelcase_sanitize_param}}.{{name}}, jsonSerializerOptions);
+            }
+
+            {{/isContainer}}
+            {{/isModel}}
+            {{/vendorExtensions.x-duplicated-data-type}}
+            {{/oneOf}}
+            {{/composedSchemas}}
+            {{/model.discriminator}}
 
             {{#model.discriminator}}
             {{#model.hasDiscriminatorWithNonEmptyMapping}}
diff --git a/samples/client/petstore/csharp/generichost/net8/OneOf/src/Org.OpenAPITools.Test/Model/FruitTests.cs b/samples/client/petstore/csharp/generichost/net8/OneOf/src/Org.OpenAPITools.Test/Model/FruitTests.cs
index a6607ae5d56d..8eb2a2d59126 100644
--- a/samples/client/petstore/csharp/generichost/net8/OneOf/src/Org.OpenAPITools.Test/Model/FruitTests.cs
+++ b/samples/client/petstore/csharp/generichost/net8/OneOf/src/Org.OpenAPITools.Test/Model/FruitTests.cs
@@ -17,6 +17,7 @@
 using Org.OpenAPITools.Model;
 using Org.OpenAPITools.Client;
 using System.Reflection;
+using System.Text.Json;
 
 namespace Org.OpenAPITools.Test.Model
 {
@@ -61,5 +62,40 @@ public void ColorTest()
         {
             // TODO unit test for the property 'Color'
         }
+
+        [Fact]
+        public void SerializeOneOfReferencedObject()
+        {
+            var options = new JsonSerializerOptions();
+            options.Converters.Add(new AppleJsonConverter());
+            options.Converters.Add(new BananaJsonConverter());
+            options.Converters.Add(new FruitJsonConverter());
+            options.Converters.Add(new OrangeJsonConverter());
+
+            Fruit fruit = new Fruit(new Apple("red"));
+
+            string json = JsonSerializer.Serialize(fruit, options);
+
+            Assert.Equal("{\"kind\":\"red\"}", json);
+        }
+
+        [Fact]
+        public void SerializeOneOfReferencedObjectWithSiblingProperty()
+        {
+            var options = new JsonSerializerOptions();
+            options.Converters.Add(new AppleJsonConverter());
+            options.Converters.Add(new BananaJsonConverter());
+            options.Converters.Add(new FruitJsonConverter());
+            options.Converters.Add(new OrangeJsonConverter());
+
+            Fruit fruit = new Fruit(
+                new Apple("red"),
+                new Option<string?>("green")
+            );
+
+            string json = JsonSerializer.Serialize(fruit, options);
+
+            Assert.Equal("{\"kind\":\"red\",\"color\":\"green\"}", json);
+        }
     }
 }
diff --git a/samples/client/petstore/csharp/generichost/net8/OneOf/src/Org.OpenAPITools/Model/Fruit.cs b/samples/client/petstore/csharp/generichost/net8/OneOf/src/Org.OpenAPITools/Model/Fruit.cs
index b122efb51e3d..61cd204f6dba 100644
--- a/samples/client/petstore/csharp/generichost/net8/OneOf/src/Org.OpenAPITools/Model/Fruit.cs
+++ b/samples/client/petstore/csharp/generichost/net8/OneOf/src/Org.OpenAPITools/Model/Fruit.cs
@@ -237,6 +237,23 @@ public override Fruit Read(ref Utf8JsonReader utf8JsonReader, Type typeToConvert
         public override void Write(Utf8JsonWriter writer, Fruit fruit, JsonSerializerOptions jsonSerializerOptions)
         {
             writer.WriteStartObject();
+            if (fruit.Apple != null)
+            {
+                AppleJsonConverter appleJsonConverter = new AppleJsonConverter();
+                appleJsonConverter.WriteProperties(writer, fruit.Apple, jsonSerializerOptions);
+            }
+
+            if (fruit.Banana != null)
+            {
+                BananaJsonConverter bananaJsonConverter = new BananaJsonConverter();
+                bananaJsonConverter.WriteProperties(writer, fruit.Banana, jsonSerializerOptions);
+            }
+
+            if (fruit.Orange != null)
+            {
+                OrangeJsonConverter orangeJsonConverter = new OrangeJsonConverter();
+                orangeJsonConverter.WriteProperties(writer, fruit.Orange, jsonSerializerOptions);
+            }
 
             WriteProperties(writer, fruit, jsonSerializerOptions);
             writer.WriteEndObject();