diff --git a/packages/eslint-plugin/src/rules/consistent-indexed-object-style.ts b/packages/eslint-plugin/src/rules/consistent-indexed-object-style.ts
index bd48718c68b..f1cf4b01eed 100644
--- a/packages/eslint-plugin/src/rules/consistent-indexed-object-style.ts
+++ b/packages/eslint-plugin/src/rules/consistent-indexed-object-style.ts
@@ -115,6 +115,9 @@ export default createRule<Options, MessageIds>({
       },
 
       TSInterfaceDeclaration(node): void {
+        if (node.extends?.length) {
+          return;
+        }
         let genericTypes = '';
 
         if ((node.typeParameters?.params ?? []).length > 0) {
diff --git a/packages/eslint-plugin/tests/rules/consistent-indexed-object-style.test.ts b/packages/eslint-plugin/tests/rules/consistent-indexed-object-style.test.ts
index 31077fcf620..44829032da3 100644
--- a/packages/eslint-plugin/tests/rules/consistent-indexed-object-style.test.ts
+++ b/packages/eslint-plugin/tests/rules/consistent-indexed-object-style.test.ts
@@ -76,7 +76,11 @@ interface Foo {
   [];
 }
     `,
-
+    `
+interface B extends A {
+  [index: number]: unknown;
+}
+    `,
     // 'index-signature'
     // Unhandled type
     {