diff --git a/src/Builder/InputObjectBuilder.php b/src/Builder/InputObjectBuilder.php
index 100e27c..02c77cd 100644
--- a/src/Builder/InputObjectBuilder.php
+++ b/src/Builder/InputObjectBuilder.php
@@ -17,6 +17,8 @@ class InputObjectBuilder extends TypeBuilder
     /** @var callable():array<FieldConfig>|array<FieldConfig> */
     private $fields = [];
 
+    private bool $isOneOf = false;
+
     final private function __construct(private string|null $name)
     {
     }
@@ -39,6 +41,13 @@ public function setFields(callable|array $fields): self
         return $this;
     }
 
+    public function isOneOf(): self
+    {
+        $this->isOneOf = true;
+
+        return $this;
+    }
+
     /** @phpstan-return InputObjectConfig */
     public function build(): array
     {
@@ -46,6 +55,7 @@ public function build(): array
             'name' => $this->name,
             'description' => $this->description,
             'fields' => $this->fields,
+            'isOneOf' => $this->isOneOf,
         ];
     }
 }
diff --git a/tests/Builder/InputObjectBuilderTest.php b/tests/Builder/InputObjectBuilderTest.php
index c549cc3..2b33e3f 100644
--- a/tests/Builder/InputObjectBuilderTest.php
+++ b/tests/Builder/InputObjectBuilderTest.php
@@ -39,6 +39,7 @@ public function __construct()
                     new InputObjectField(InputFieldBuilder::create('Another', Type::string())->build()),
                 ],
             )
+            ->isOneOf()
             ->build();
 
         self::assertArrayHasKey('name', $object);
@@ -47,5 +48,7 @@ public function __construct()
         self::assertSame($description, $object['description']);
         self::assertIsArray($object['fields']);
         self::assertCount(2, $object['fields']);
+        self::assertArrayHasKey('isOneOf', $object);
+        self::assertTrue($object['isOneOf']);
     }
 }