diff --git a/packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/src/Providers/RestClientProvider.cs b/packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/src/Providers/RestClientProvider.cs
index 5cee8c429b3..0c442c416bc 100644
--- a/packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/src/Providers/RestClientProvider.cs
+++ b/packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/src/Providers/RestClientProvider.cs
@@ -637,9 +637,9 @@ private static MethodBodyStatement BuildAppendQueryStatement(
                         valueExpression.AsDictionary(paramType),
                         out KeyValuePairExpression item);
                     var convertedItem = paramType.ElementType.IsEnum
-                        ? paramType.ElementType.ToSerial(item)
+                        ? paramType.ElementType.ToSerial(item.Value)
                         : item.Value;
-                    forEachStatement.Add(uri.AppendQuery(item.Key, convertedItem, true).Terminate());
+                    AddExplodeQueryItem(forEachStatement, uri, item.Key, convertedItem, paramType.ElementType);
                     return forEachStatement;
                 }
                 else
@@ -674,11 +674,35 @@ private static MethodBodyStatement BuildAppendQueryStatement(
                 {
                     convertedItem = item;
                 }
-                forEachStatement.Add(uri.AppendQuery(Literal(inputQueryParameter.SerializedName), convertedItem, true).Terminate());
+                AddExplodeQueryItem(forEachStatement, uri, Literal(inputQueryParameter.SerializedName), convertedItem, paramType.ElementType);
                 return forEachStatement;
             }
         }
 
+        private static bool IsExtensibleStringEnum(CSharpType type)
+            => type.IsEnum && type.IsStruct && type.UnderlyingEnumType == typeof(string);
+
+        private static void AddExplodeQueryItem(
+            ForEachStatement forEachStatement,
+            ScopedApi uri,
+            ValueExpression key,
+            ValueExpression convertedItem,
+            CSharpType elementType)
+        {
+            if (IsExtensibleStringEnum(elementType))
+            {
+                forEachStatement.Add(Declare("paramStr", typeof(string), convertedItem, out VariableExpression cachedVar));
+                forEachStatement.Add(new IfStatement(cachedVar.As<string>().NotEqual(Null))
+                {
+                    uri.AppendQuery(key, cachedVar, true).Terminate()
+                });
+            }
+            else
+            {
+                forEachStatement.Add(uri.AppendQuery(key, convertedItem, true).Terminate());
+            }
+        }
+
         /// <summary>
         /// Builds the statements for a model-typed query parameter that uses form-style `explode`.
         /// Each (simple) property of the model is emitted as its own query entry using the property's
diff --git a/packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/RestClientProviders/RestClientProviderTests.cs b/packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/RestClientProviders/RestClientProviderTests.cs
index 07de6b5411a..1239e640469 100644
--- a/packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/RestClientProviders/RestClientProviderTests.cs
+++ b/packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/RestClientProviders/RestClientProviderTests.cs
@@ -1054,6 +1054,10 @@ public void TestBuildCreateRequestMethodWithQueryParameters()
             var inputStringEnum = InputFactory.StringEnum(
                 "foo",
                 stringEnumValues);
+            var inputExtensibleStringEnum = InputFactory.StringEnum(
+                "extensibleFoo",
+                stringEnumValues,
+                isExtensible: true);
             var inputIntEnum = InputFactory.Int32Enum(
                 "intFoo",
                 intEnumValues);
@@ -1078,6 +1082,10 @@ public void TestBuildCreateRequestMethodWithQueryParameters()
                 InputFactory.QueryParameter("p7Explode", InputFactory.Dictionary(inputIntEnum), isRequired: true, explode: true),
                 InputFactory.QueryParameter("p8Explode", InputFactory.Array(inputFloatEnum), isRequired: true, explode: true),
                 InputFactory.QueryParameter("p9Explode", InputFactory.Array(inputDoubleEnum), isRequired: true, explode: true),
+                InputFactory.QueryParameter("p10Explode", InputFactory.Array(inputExtensibleStringEnum), isRequired: true, explode: true),
+                InputFactory.QueryParameter("p11Explode", InputFactory.Dictionary(inputExtensibleStringEnum), isRequired: true, explode: true),
+                InputFactory.QueryParameter("p12", inputExtensibleStringEnum, isRequired: true),
+                InputFactory.QueryParameter("p13", new InputNullableType(inputExtensibleStringEnum), isRequired: false),
             ];
             var operation = InputFactory.Operation(
                 "sampleOp",
diff --git a/packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/RestClientProviders/TestData/RestClientProviderTests/TestBuildCreateRequestMethodWithQueryParameters.cs b/packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/RestClientProviders/TestData/RestClientProviderTests/TestBuildCreateRequestMethodWithQueryParameters.cs
index 60b5383a969..ed43cefed82 100644
--- a/packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/RestClientProviders/TestData/RestClientProviderTests/TestBuildCreateRequestMethodWithQueryParameters.cs
+++ b/packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/RestClientProviders/TestData/RestClientProviderTests/TestBuildCreateRequestMethodWithQueryParameters.cs
@@ -10,7 +10,7 @@ namespace Sample
 {
     public partial class TestClient
     {
-        internal global::System.ClientModel.Primitives.PipelineMessage CreateSampleOpRequest(global::System.Collections.Generic.IEnumerable<string> p1Explode, global::System.Collections.Generic.IEnumerable<string> p1, global::System.Collections.Generic.IEnumerable<int> p2Explode, global::System.Collections.Generic.IEnumerable<int> p2, global::System.Collections.Generic.IDictionary<string, int> p3Explode, global::System.Collections.Generic.IDictionary<string, int> p3, global::System.Collections.Generic.IEnumerable<global::Sample.Models.Foo> p4Explode, global::System.Collections.Generic.IEnumerable<global::Sample.Models.IntFoo> p5Explode, global::System.Collections.Generic.IDictionary<string, global::Sample.Models.Foo> p6Explode, global::System.Collections.Generic.IDictionary<string, global::Sample.Models.IntFoo> p7Explode, global::System.Collections.Generic.IEnumerable<global::Sample.Models.FloatFoo> p8Explode, global::System.Collections.Generic.IEnumerable<global::Sample.Models.DoubleFoo> p9Explode, string optionalParam, global::System.ClientModel.Primitives.RequestOptions options)
+        internal global::System.ClientModel.Primitives.PipelineMessage CreateSampleOpRequest(global::System.Collections.Generic.IEnumerable<string> p1Explode, global::System.Collections.Generic.IEnumerable<string> p1, global::System.Collections.Generic.IEnumerable<int> p2Explode, global::System.Collections.Generic.IEnumerable<int> p2, global::System.Collections.Generic.IDictionary<string, int> p3Explode, global::System.Collections.Generic.IDictionary<string, int> p3, global::System.Collections.Generic.IEnumerable<global::Sample.Models.Foo> p4Explode, global::System.Collections.Generic.IEnumerable<global::Sample.Models.IntFoo> p5Explode, global::System.Collections.Generic.IDictionary<string, global::Sample.Models.Foo> p6Explode, global::System.Collections.Generic.IDictionary<string, global::Sample.Models.IntFoo> p7Explode, global::System.Collections.Generic.IEnumerable<global::Sample.Models.FloatFoo> p8Explode, global::System.Collections.Generic.IEnumerable<global::Sample.Models.DoubleFoo> p9Explode, global::System.Collections.Generic.IEnumerable<global::Sample.Models.ExtensibleFoo> p10Explode, global::System.Collections.Generic.IDictionary<string, global::Sample.Models.ExtensibleFoo> p11Explode, string p12, string optionalParam, string p13, global::System.ClientModel.Primitives.RequestOptions options)
         {
             global::Sample.ClientUriBuilder uri = new global::Sample.ClientUriBuilder();
             uri.Reset(_endpoint);
@@ -75,14 +75,14 @@ public partial class TestClient
             {
                 foreach (var @param in p6Explode)
                 {
-                    uri.AppendQuery(@param.Key, @param.ToSerialString(), true);
+                    uri.AppendQuery(@param.Key, @param.Value.ToSerialString(), true);
                 }
             }
             if (((p7Explode != null) && !((p7Explode is global::Sample.ChangeTrackingDictionary<string, global::Sample.Models.IntFoo> changeTrackingDictionary2) && changeTrackingDictionary2.IsUndefined)))
             {
                 foreach (var @param in p7Explode)
                 {
-                    uri.AppendQuery(@param.Key, ((int)@param), true);
+                    uri.AppendQuery(@param.Key, ((int)@param.Value), true);
                 }
             }
             if (((p8Explode != null) && !((p8Explode is global::Sample.ChangeTrackingList<global::Sample.Models.FloatFoo> changeTrackingList5) && changeTrackingList5.IsUndefined)))
@@ -99,6 +99,33 @@ public partial class TestClient
                     uri.AppendQuery("p9Explode", ((double)@param), true);
                 }
             }
+            if (((p10Explode != null) && !((p10Explode is global::Sample.ChangeTrackingList<global::Sample.Models.ExtensibleFoo> changeTrackingList7) && changeTrackingList7.IsUndefined)))
+            {
+                foreach (var @param in p10Explode)
+                {
+                    string paramStr = @param.ToString();
+                    if ((paramStr != null))
+                    {
+                        uri.AppendQuery("p10Explode", paramStr, true);
+                    }
+                }
+            }
+            if (((p11Explode != null) && !((p11Explode is global::Sample.ChangeTrackingDictionary<string, global::Sample.Models.ExtensibleFoo> changeTrackingDictionary3) && changeTrackingDictionary3.IsUndefined)))
+            {
+                foreach (var @param in p11Explode)
+                {
+                    string paramStr = @param.Value.ToString();
+                    if ((paramStr != null))
+                    {
+                        uri.AppendQuery(@param.Key, paramStr, true);
+                    }
+                }
+            }
+            uri.AppendQuery("p12", p12, true);
+            if ((p13 != null))
+            {
+                uri.AppendQuery("p13", p13, true);
+            }
             global::System.ClientModel.Primitives.PipelineMessage message = Pipeline.CreateMessage(uri.ToUri(), "GET", PipelineMessageClassifier200);
             global::System.ClientModel.Primitives.PipelineRequest request = message.Request;
             message.Apply(options);