diff --git a/packages/eslint-plugin/src/rules/prefer-readonly.ts b/packages/eslint-plugin/src/rules/prefer-readonly.ts
index c82aaf45ab3..451515d18ed 100644
--- a/packages/eslint-plugin/src/rules/prefer-readonly.ts
+++ b/packages/eslint-plugin/src/rules/prefer-readonly.ts
@@ -179,7 +179,7 @@ export default util.createRule<Options, MessageIds>({
         const tsNode = parserServices.esTreeNodeToTSNodeMap.get<
           ts.PropertyAccessExpression
         >(node);
-        if (classScopeStack.length !== 0) {
+        if (classScopeStack.length !== 0 && !node.computed) {
           handlePropertyAccessExpression(
             tsNode,
             tsNode.parent,
diff --git a/packages/eslint-plugin/tests/rules/prefer-readonly.test.ts b/packages/eslint-plugin/tests/rules/prefer-readonly.test.ts
index a5ff4734e1c..5b2a6687339 100644
--- a/packages/eslint-plugin/tests/rules/prefer-readonly.test.ts
+++ b/packages/eslint-plugin/tests/rules/prefer-readonly.test.ts
@@ -215,6 +215,11 @@ ruleTester.run('prefer-readonly', rule, {
         },
       ],
     },
+    `class TestComputedParameter {
+      public mutate() {
+        this['computed'] = 1;
+      }
+    }`,
   ],
   invalid: [
     {