diff --git a/src/validation/__tests__/KnownDirectivesRule-test.ts b/src/validation/__tests__/KnownDirectivesRule-test.ts
index e36761fbef..38173f1cd3 100644
--- a/src/validation/__tests__/KnownDirectivesRule-test.ts
+++ b/src/validation/__tests__/KnownDirectivesRule-test.ts
@@ -325,7 +325,9 @@ describe('Validate: Known directives', () => {
             myField(myArg: Int @onArgumentDefinition): String @onFieldDefinition
           }
 
-          extend type MyObj @onObject
+          extend type MyObj @onObject {
+            myExtensionField(myArg: Int @onArgumentDefinition): String @onFieldDefinition
+          }
 
           scalar MyScalar @onScalar
 
@@ -335,7 +337,9 @@ describe('Validate: Known directives', () => {
             myField(myArg: Int @onArgumentDefinition): String @onFieldDefinition
           }
 
-          extend interface MyInterface @onInterface
+          extend interface MyInterface @onInterface {
+            myExtensionField(myArg: Int @onArgumentDefinition): String @onFieldDefinition
+          }
 
           union MyUnion @onUnion = MyObj | Other
 
@@ -351,7 +355,9 @@ describe('Validate: Known directives', () => {
             myField: Int @onInputFieldDefinition
           }
 
-          extend input MyInput @onInputObject
+          extend input MyInput @onInputObject {
+            myExtensionField: Int @onInputFieldDefinition
+          }
 
           schema @onSchema {
             query: MyQuery
@@ -375,12 +381,20 @@ describe('Validate: Known directives', () => {
             myField(myArg: Int @onInputFieldDefinition): String @onInputFieldDefinition
           }
 
+          extend type MyObj @onDirective {
+            myExtensionField(myArg: Int @onInputFieldDefinition): String @onInputFieldDefinition
+          }
+
           scalar MyScalar @onEnum
 
           interface MyInterface @onObject {
             myField(myArg: Int @onInputFieldDefinition): String @onInputFieldDefinition
           }
 
+          extend interface MyInterface @onObject {
+            myExtensionField(myArg: Int @onInputFieldDefinition): String @onInputFieldDefinition
+          }
+
           union MyUnion @onEnumValue = MyObj | Other
 
           enum MyEnum @onScalar {
@@ -391,13 +405,15 @@ describe('Validate: Known directives', () => {
             myField: Int @onArgumentDefinition
           }
 
+          extend input MyInput {
+            myExtensionField: Int @onArgumentDefinition
+          }
+
           schema @onObject {
             query: MyQuery
           }
 
           extend schema @onObject
-
-          extend type MyObj @onDirective
         `,
         schemaWithSDLDirectives,
       ).toDeepEqual([
@@ -415,56 +431,85 @@ describe('Validate: Known directives', () => {
             'Directive "@onInputFieldDefinition" may not be used on FIELD_DEFINITION.',
           locations: [{ line: 3, column: 65 }],
         },
+        {
+          message: 'Directive "@onDirective" may not be used on OBJECT.',
+          locations: [{ line: 6, column: 29 }],
+        },
+        {
+          message:
+            'Directive "@onInputFieldDefinition" may not be used on ARGUMENT_DEFINITION.',
+          locations: [{ line: 7, column: 41 }],
+        },
+        {
+          message:
+            'Directive "@onInputFieldDefinition" may not be used on FIELD_DEFINITION.',
+          locations: [{ line: 7, column: 74 }],
+        },
         {
           message: 'Directive "@onEnum" may not be used on SCALAR.',
-          locations: [{ line: 6, column: 27 }],
+          locations: [{ line: 10, column: 27 }],
         },
         {
           message: 'Directive "@onObject" may not be used on INTERFACE.',
-          locations: [{ line: 8, column: 33 }],
+          locations: [{ line: 12, column: 33 }],
         },
         {
           message:
             'Directive "@onInputFieldDefinition" may not be used on ARGUMENT_DEFINITION.',
-          locations: [{ line: 9, column: 32 }],
+          locations: [{ line: 13, column: 32 }],
         },
         {
           message:
             'Directive "@onInputFieldDefinition" may not be used on FIELD_DEFINITION.',
-          locations: [{ line: 9, column: 65 }],
+          locations: [{ line: 13, column: 65 }],
+        },
+        {
+          message: 'Directive "@onObject" may not be used on INTERFACE.',
+          locations: [{ line: 16, column: 40 }],
+        },
+        {
+          message:
+            'Directive "@onInputFieldDefinition" may not be used on ARGUMENT_DEFINITION.',
+          locations: [{ line: 17, column: 41 }],
+        },
+        {
+          message:
+            'Directive "@onInputFieldDefinition" may not be used on FIELD_DEFINITION.',
+          locations: [{ line: 17, column: 74 }],
         },
         {
           message: 'Directive "@onEnumValue" may not be used on UNION.',
-          locations: [{ line: 12, column: 25 }],
+          locations: [{ line: 20, column: 25 }],
         },
         {
           message: 'Directive "@onScalar" may not be used on ENUM.',
-          locations: [{ line: 14, column: 23 }],
+          locations: [{ line: 22, column: 23 }],
         },
         {
           message: 'Directive "@onUnion" may not be used on ENUM_VALUE.',
-          locations: [{ line: 15, column: 22 }],
+          locations: [{ line: 23, column: 22 }],
         },
         {
           message: 'Directive "@onEnum" may not be used on INPUT_OBJECT.',
-          locations: [{ line: 18, column: 25 }],
+          locations: [{ line: 26, column: 25 }],
         },
         {
           message:
             'Directive "@onArgumentDefinition" may not be used on INPUT_FIELD_DEFINITION.',
-          locations: [{ line: 19, column: 26 }],
+          locations: [{ line: 27, column: 26 }],
         },
         {
-          message: 'Directive "@onObject" may not be used on SCHEMA.',
-          locations: [{ line: 22, column: 18 }],
+          message:
+            'Directive "@onArgumentDefinition" may not be used on INPUT_FIELD_DEFINITION.',
+          locations: [{ line: 31, column: 35 }],
         },
         {
           message: 'Directive "@onObject" may not be used on SCHEMA.',
-          locations: [{ line: 26, column: 25 }],
+          locations: [{ line: 34, column: 18 }],
         },
         {
-          message: 'Directive "@onDirective" may not be used on OBJECT.',
-          locations: [{ line: 28, column: 29 }],
+          message: 'Directive "@onObject" may not be used on SCHEMA.',
+          locations: [{ line: 38, column: 25 }],
         },
       ]);
     });
diff --git a/src/validation/rules/KnownDirectivesRule.ts b/src/validation/rules/KnownDirectivesRule.ts
index 320ecf64a1..84e77b8c8e 100644
--- a/src/validation/rules/KnownDirectivesRule.ts
+++ b/src/validation/rules/KnownDirectivesRule.ts
@@ -153,7 +153,8 @@ function getDirectiveLocationForASTPath(
     case Kind.INPUT_VALUE_DEFINITION: {
       const parentNode = ancestors.at(-3);
       invariant(parentNode != null && 'kind' in parentNode);
-      return parentNode.kind === Kind.INPUT_OBJECT_TYPE_DEFINITION
+      return parentNode.kind === Kind.INPUT_OBJECT_TYPE_DEFINITION ||
+        parentNode.kind === Kind.INPUT_OBJECT_TYPE_EXTENSION
         ? DirectiveLocation.INPUT_FIELD_DEFINITION
         : DirectiveLocation.ARGUMENT_DEFINITION;
     }