diff --git a/src/Type/Introspection.php b/src/Type/Introspection.php
index cf26e0758..32ebef872 100644
--- a/src/Type/Introspection.php
+++ b/src/Type/Introspection.php
@@ -115,6 +115,7 @@ public static function getIntrospectionQuery(array $options = []): string
     kind
     name
     {$descriptions}
+    isOneOf
     fields(includeDeprecated: true) {
       name
       {$descriptions}
diff --git a/tests/Type/IntrospectionTest.php b/tests/Type/IntrospectionTest.php
index be5a17328..b2aa5452a 100644
--- a/tests/Type/IntrospectionTest.php
+++ b/tests/Type/IntrospectionTest.php
@@ -53,6 +53,7 @@ public function testExecutesAnIntrospectionQuery(): void
                         [
                             'kind' => 'OBJECT',
                             'name' => 'SomeObject',
+                            'isOneOf' => null,
                             'fields' => [
                                 [
                                     'name' => 'someField',
@@ -74,6 +75,7 @@ public function testExecutesAnIntrospectionQuery(): void
                         [
                             'kind' => 'SCALAR',
                             'name' => 'String',
+                            'isOneOf' => null,
                             'fields' => null,
                             'inputFields' => null,
                             'interfaces' => null,
@@ -83,6 +85,7 @@ public function testExecutesAnIntrospectionQuery(): void
                         [
                             'kind' => 'SCALAR',
                             'name' => 'Boolean',
+                            'isOneOf' => null,
                             'fields' => null,
                             'inputFields' => null,
                             'interfaces' => null,
@@ -92,6 +95,7 @@ public function testExecutesAnIntrospectionQuery(): void
                         [
                             'kind' => 'OBJECT',
                             'name' => '__Schema',
+                            'isOneOf' => null,
                             'fields' => [
                                 0 => [
                                     'name' => 'types',
@@ -185,6 +189,7 @@ public function testExecutesAnIntrospectionQuery(): void
                         [
                             'kind' => 'OBJECT',
                             'name' => '__Type',
+                            'isOneOf' => null,
                             'fields' => [
                                 0 => [
                                     'name' => 'kind',
@@ -385,6 +390,7 @@ public function testExecutesAnIntrospectionQuery(): void
                         [
                             'kind' => 'ENUM',
                             'name' => '__TypeKind',
+                            'isOneOf' => null,
                             'fields' => null,
                             'inputFields' => null,
                             'interfaces' => null,
@@ -435,6 +441,7 @@ public function testExecutesAnIntrospectionQuery(): void
                         [
                             'kind' => 'OBJECT',
                             'name' => '__Field',
+                            'isOneOf' => null,
                             'fields' => [
                                 0 => [
                                     'name' => 'name',
@@ -547,6 +554,7 @@ public function testExecutesAnIntrospectionQuery(): void
                         [
                             'kind' => 'OBJECT',
                             'name' => '__InputValue',
+                            'isOneOf' => null,
                             'fields' => [
                                 0 => [
                                     'name' => 'name',
@@ -635,6 +643,7 @@ public function testExecutesAnIntrospectionQuery(): void
                         [
                             'kind' => 'OBJECT',
                             'name' => '__EnumValue',
+                            'isOneOf' => null,
                             'fields' => [
                                 0 => [
                                     'name' => 'name',
@@ -697,6 +706,7 @@ public function testExecutesAnIntrospectionQuery(): void
                         [
                             'kind' => 'OBJECT',
                             'name' => '__Directive',
+                            'isOneOf' => null,
                             'fields' => [
                                 [
                                     'name' => 'name',
@@ -794,6 +804,7 @@ public function testExecutesAnIntrospectionQuery(): void
                         [
                             'kind' => 'ENUM',
                             'name' => '__DirectiveLocation',
+                            'isOneOf' => null,
                             'fields' => null,
                             'inputFields' => null,
                             'interfaces' => null,
@@ -1831,4 +1842,30 @@ public static function invisibleFieldDataProvider(): iterable
         yield [fn (): bool => false];
         yield [false];
     }
+
+    public function testIsOneOf(): void
+    {
+        $input = new InputObjectType([
+            'name' => 'SearchInput',
+            'isOneOf' => true,
+            'fields' => [
+                'name' => ['type' => Type::string()],
+                'email' => ['type' => Type::string()],
+            ],
+        ]);
+
+        $query = new ObjectType([
+            'name' => 'QueryRoot',
+            'fields' => [
+                'input' => ['type' => $input],
+            ],
+        ]);
+
+        $schema = new Schema([
+            'query' => $query,
+        ]);
+
+        $introspection = Introspection::fromSchema($schema);
+        self::assertTrue($introspection['__schema']['types'][1]['isOneOf']);
+    }
 }
diff --git a/tests/Validator/QueryComplexityTest.php b/tests/Validator/QueryComplexityTest.php
index 8ea6da018..57269c357 100644
--- a/tests/Validator/QueryComplexityTest.php
+++ b/tests/Validator/QueryComplexityTest.php
@@ -164,7 +164,7 @@ public function testQueryWithCustomAndSkipDirective(): void
 
     public function testComplexityIntrospectionQuery(): void
     {
-        $this->assertIntrospectionQuery(187);
+        $this->assertIntrospectionQuery(188);
     }
 
     public function testIntrospectionTypeMetaFieldQuery(): void