diff --git a/graphql-dgs-codegen-core/src/main/kotlin/com/netflix/graphql/dgs/codegen/CodeGen.kt b/graphql-dgs-codegen-core/src/main/kotlin/com/netflix/graphql/dgs/codegen/CodeGen.kt
index bbc474e4..cbd181ae 100644
--- a/graphql-dgs-codegen-core/src/main/kotlin/com/netflix/graphql/dgs/codegen/CodeGen.kt
+++ b/graphql-dgs-codegen-core/src/main/kotlin/com/netflix/graphql/dgs/codegen/CodeGen.kt
@@ -210,7 +210,7 @@ class CodeGen(private val config: CodeGenConfig) {
             .filterIsInstance<UnionTypeDefinition>()
             .excludeSchemaTypeExtension()
             .filter { config.generateDataTypes || config.generateInterfaces || it.name in requiredTypeCollector.requiredTypes }
-            .map { UnionTypeGenerator(config).generate(it, findUnionExtensions(it.name, definitions)) }
+            .map { UnionTypeGenerator(config, document).generate(it, findUnionExtensions(it.name, definitions)) }
             .fold(CodeGenResult()) { t: CodeGenResult, u: CodeGenResult -> t.merge(u) }
     }
 
diff --git a/graphql-dgs-codegen-core/src/main/kotlin/com/netflix/graphql/dgs/codegen/generators/java/UnionTypeGenerator.kt b/graphql-dgs-codegen-core/src/main/kotlin/com/netflix/graphql/dgs/codegen/generators/java/UnionTypeGenerator.kt
index 0acd512c..6e514ae6 100644
--- a/graphql-dgs-codegen-core/src/main/kotlin/com/netflix/graphql/dgs/codegen/generators/java/UnionTypeGenerator.kt
+++ b/graphql-dgs-codegen-core/src/main/kotlin/com/netflix/graphql/dgs/codegen/generators/java/UnionTypeGenerator.kt
@@ -24,12 +24,17 @@ import com.netflix.graphql.dgs.codegen.shouldSkip
 import com.squareup.javapoet.ClassName
 import com.squareup.javapoet.JavaFile
 import com.squareup.javapoet.TypeSpec
+import graphql.language.Document
 import graphql.language.TypeName
 import graphql.language.UnionTypeDefinition
 import graphql.language.UnionTypeExtensionDefinition
 import javax.lang.model.element.Modifier
 
-class UnionTypeGenerator(private val config: CodeGenConfig) {
+class UnionTypeGenerator(private val config: CodeGenConfig, private val document: Document) {
+
+    val packageName = config.packageNameTypes
+    private val typeUtils = TypeUtils(packageName, config, document)
+
     fun generate(definition: UnionTypeDefinition, extensions: List<UnionTypeExtensionDefinition>): CodeGenResult {
         if (definition.shouldSkip(config)) {
             return CodeGenResult()
@@ -41,7 +46,10 @@ class UnionTypeGenerator(private val config: CodeGenConfig) {
 
         val memberTypes = definition.memberTypes.plus(extensions.flatMap { it.memberTypes }).asSequence()
             .filterIsInstance<TypeName>()
-            .map { member -> ClassName.get(packageName, member.name) }
+            .map { member ->
+                typeUtils.findJavaInterfaceName(member.name, packageName)
+            }
+            .filterIsInstance<ClassName>()
             .toList()
 
         if (memberTypes.isNotEmpty()) {
@@ -52,6 +60,4 @@ class UnionTypeGenerator(private val config: CodeGenConfig) {
         val javaFile = JavaFile.builder(packageName, javaType.build()).build()
         return CodeGenResult(javaInterfaces = listOf(javaFile))
     }
-
-    val packageName = config.packageNameTypes
 }
diff --git a/graphql-dgs-codegen-core/src/test/kotlin/com/netflix/graphql/dgs/codegen/CodeGenTest.kt b/graphql-dgs-codegen-core/src/test/kotlin/com/netflix/graphql/dgs/codegen/CodeGenTest.kt
index f469ee49..ec2a5345 100644
--- a/graphql-dgs-codegen-core/src/test/kotlin/com/netflix/graphql/dgs/codegen/CodeGenTest.kt
+++ b/graphql-dgs-codegen-core/src/test/kotlin/com/netflix/graphql/dgs/codegen/CodeGenTest.kt
@@ -4530,6 +4530,36 @@ It takes a title and such.
         assertThat(dataTypes[1].typeSpec.superinterfaces[0].toString()).isEqualTo("java.lang.String")
     }
 
+    @Test
+    fun `Supports typeMapping in union type generation`() {
+        val schema = """
+            type A {
+                name: String
+            }
+        
+            type B {
+                count: Int
+            }
+        
+            union C = A | B
+        """.trimIndent()
+
+        val result = CodeGen(
+            CodeGenConfig(
+                schemas = setOf(schema),
+                packageName = basePackageName,
+                typeMapping = mapOf(
+                    "A" to "java.lang.String"
+                )
+            )
+        ).generate()
+
+        assertThat(result.javaDataTypes.size).isEqualTo(1)
+
+        assertThat(result.javaDataTypes[0].typeSpec.superinterfaces[0].toString()).isEqualTo("com.netflix.graphql.dgs.codegen.tests.generated.types.C")
+        assertCompilesJava(result)
+    }
+
     @Test
     fun `The default value for Locale should be overridden and wrapped`() {
         val schema = """