diff --git a/packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator/test/Providers/ModelFactories/ModelFactoriesCustomizationTests.cs b/packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator/test/Providers/ModelFactories/ModelFactoriesCustomizationTests.cs
index c35f1968d76..d58fa5e3fb4 100644
--- a/packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator/test/Providers/ModelFactories/ModelFactoriesCustomizationTests.cs
+++ b/packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator/test/Providers/ModelFactories/ModelFactoriesCustomizationTests.cs
@@ -2,6 +2,7 @@
 // Licensed under the MIT License.
 
 using System;
+using System.Collections.Generic;
 using System.Linq;
 using System.Threading.Tasks;
 using Microsoft.CodeAnalysis;
@@ -203,6 +204,66 @@ public async Task OmitsModelFactoryMethodIfDerivedModelTypeInternal()
             CollectionAssert.DoesNotContain(modelFactory.Methods.Select(m => m.Signature.Name), "DerivedModel");
         }
 
+        [Test]
+        public async Task CustomFullConstructorFactoryMethodRetainsGeneratedModelParameterNamespaces()
+        {
+            var networkSubResource = InputFactory.Model("NetworkSubResource");
+            var association = InputFactory.Model("EffectiveNetworkSecurityGroupAssociation");
+            var rule = InputFactory.Model("EffectiveNetworkSecurityRule");
+            var effectiveNetworkSecurityGroup = InputFactory.Model(
+                "EffectiveNetworkSecurityGroup",
+                properties:
+                [
+                    InputFactory.Property("NetworkSecurityGroup", networkSubResource),
+                    InputFactory.Property("Association", association),
+                    InputFactory.Property("EffectiveSecurityRules", InputFactory.Array(rule)),
+                    InputFactory.Property("TagMap", InputPrimitiveType.String),
+                ]);
+
+            var mockGenerator = await MockHelpers.LoadMockGeneratorAsync(
+                inputNamespaceName: "Sample.Namespace",
+                inputModelTypes: [networkSubResource, association, rule, effectiveNetworkSecurityGroup],
+                compilation: async () => await Helpers.GetCompilationFromDirectoryAsync(),
+                additionalMetadataReferences: [MetadataReference.CreateFromFile(typeof(BinaryData).Assembly.Location)]);
+
+            var csharpGen = new CSharpGen();
+            await csharpGen.ExecuteAsync();
+
+            var modelProvider = mockGenerator.Object.OutputLibrary.TypeProviders
+                .OfType<ModelProvider>()
+                .Single(m => m.Name == "EffectiveNetworkSecurityGroup");
+            Assert.IsFalse(
+                modelProvider.Constructors.Contains(modelProvider.FullConstructor),
+                $"The generated full constructor should be suppressed. Actual signature: {string.Join(", ", modelProvider.FullConstructor.Signature.Parameters.Select(p => p.Type.ToString()))}");
+            Assert.IsTrue(modelProvider.CanonicalView.Constructors.Any(c => c.EnclosingType == modelProvider.CustomCodeView), "The custom internal constructor should replace the suppressed full constructor.");
+
+            var modelFactory = mockGenerator.Object.OutputLibrary.TypeProviders.SingleOrDefault(t => t is ModelFactoryProvider);
+            Assert.IsNotNull(modelFactory);
+
+            var customFactoryMethod = modelFactory!.CustomCodeView!.Methods
+                .Single(m => m.Signature.Name == "EffectiveNetworkSecurityGroup");
+            Assert.AreEqual(3, customFactoryMethod.Signature.Parameters.Count);
+
+            var generatedFactoryMethod = modelFactory.Methods
+                .SingleOrDefault(m => m.Signature.Name == "EffectiveNetworkSecurityGroup");
+            Assert.IsNotNull(generatedFactoryMethod);
+            Assert.AreEqual(4, generatedFactoryMethod!.Signature.Parameters.Count);
+
+            var content = new TypeProviderWriter(modelFactory).Write().Content;
+            Assert.IsFalse(content.Contains("using ;"), $"Model factory wrote an empty using directive:\n{content}");
+            Assert.IsFalse(content.Contains("global::."), $"Model factory wrote an empty-namespace type reference:\n{content}");
+
+            var networkSecurityGroupParam = generatedFactoryMethod.Signature.Parameters.Single(p => p.Name == "networkSecurityGroup");
+            Assert.AreEqual("Sample.Models", networkSecurityGroupParam.Type.Namespace);
+
+            var associationParam = generatedFactoryMethod.Signature.Parameters.Single(p => p.Name == "association");
+            Assert.AreEqual("Sample.Models", associationParam.Type.Namespace);
+
+            var effectiveSecurityRulesParam = generatedFactoryMethod.Signature.Parameters.Single(p => p.Name == "effectiveSecurityRules");
+            Assert.AreEqual(typeof(IEnumerable<>), effectiveSecurityRulesParam.Type.FrameworkType);
+            Assert.AreEqual("Sample.Models", effectiveSecurityRulesParam.Type.Arguments[0].Namespace);
+        }
+
         [TestCase(true)]
         [TestCase(false)]
         public async Task CanCustomizeModelFullConstructor(bool extraParameters)
diff --git a/packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator/test/Providers/ModelFactories/TestData/ModelFactoriesCustomizationTests/CustomFullConstructorFactoryMethodRetainsGeneratedModelParameterNamespaces/EffectiveNetworkSecurityGroup.cs b/packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator/test/Providers/ModelFactories/TestData/ModelFactoriesCustomizationTests/CustomFullConstructorFactoryMethodRetainsGeneratedModelParameterNamespaces/EffectiveNetworkSecurityGroup.cs
new file mode 100644
index 00000000000..5ff055655a7
--- /dev/null
+++ b/packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator/test/Providers/ModelFactories/TestData/ModelFactoriesCustomizationTests/CustomFullConstructorFactoryMethodRetainsGeneratedModelParameterNamespaces/EffectiveNetworkSecurityGroup.cs
@@ -0,0 +1,32 @@
+using System;
+using System.Collections.Generic;
+using Microsoft.TypeSpec.Generator.Customizations;
+using SampleTypeSpec;
+
+#nullable disable
+
+namespace Sample.Models;
+
+[CodeGenSuppress(
+    "EffectiveNetworkSecurityGroup",
+    typeof(NetworkSubResource),
+    typeof(EffectiveNetworkSecurityGroupAssociation),
+    typeof(IList<EffectiveNetworkSecurityRule>),
+    typeof(string),
+    typeof(IDictionary<string, BinaryData>))]
+public partial class EffectiveNetworkSecurityGroup
+{
+    internal EffectiveNetworkSecurityGroup(
+        NetworkSubResource networkSecurityGroup,
+        EffectiveNetworkSecurityGroupAssociation association,
+        IReadOnlyList<EffectiveNetworkSecurityRule> effectiveSecurityRules,
+        string tagMap,
+        IDictionary<string, BinaryData> additionalBinaryDataProperties)
+    {
+        NetworkSecurityGroup = networkSecurityGroup;
+        Association = association;
+        EffectiveSecurityRules = effectiveSecurityRules;
+        TagMap = tagMap;
+        _additionalBinaryDataProperties = additionalBinaryDataProperties;
+    }
+}
diff --git a/packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator/test/Providers/ModelFactories/TestData/ModelFactoriesCustomizationTests/CustomFullConstructorFactoryMethodRetainsGeneratedModelParameterNamespaces/SampleNamespaceModelFactory.cs b/packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator/test/Providers/ModelFactories/TestData/ModelFactoriesCustomizationTests/CustomFullConstructorFactoryMethodRetainsGeneratedModelParameterNamespaces/SampleNamespaceModelFactory.cs
new file mode 100644
index 00000000000..941f0613a57
--- /dev/null
+++ b/packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator/test/Providers/ModelFactories/TestData/ModelFactoriesCustomizationTests/CustomFullConstructorFactoryMethodRetainsGeneratedModelParameterNamespaces/SampleNamespaceModelFactory.cs
@@ -0,0 +1,22 @@
+using System.Collections.Generic;
+using Sample.Models;
+
+#nullable disable
+
+namespace Sample.Namespace;
+
+public static partial class SampleNamespaceModelFactory
+{
+    public static EffectiveNetworkSecurityGroup EffectiveNetworkSecurityGroup(
+        NetworkSubResource networkSecurityGroup,
+        EffectiveNetworkSecurityGroupAssociation association,
+        IReadOnlyList<EffectiveNetworkSecurityRule> effectiveSecurityRules)
+    {
+        return new EffectiveNetworkSecurityGroup(
+            networkSecurityGroup,
+            association,
+            effectiveSecurityRules,
+            tagMap: default,
+            additionalBinaryDataProperties: default);
+    }
+}