diff --git a/packages/eslint-plugin/tests/rules/prefer-readonly-parameter-types.test.ts b/packages/eslint-plugin/tests/rules/prefer-readonly-parameter-types.test.ts
index f17a19f1f6d..c8fb885a73e 100644
--- a/packages/eslint-plugin/tests/rules/prefer-readonly-parameter-types.test.ts
+++ b/packages/eslint-plugin/tests/rules/prefer-readonly-parameter-types.test.ts
@@ -222,6 +222,21 @@ ruleTester.run('prefer-readonly-parameter-types', rule, {
         },
       ],
     },
+    // PrivateIdentifier is handled without throwing error.
+    {
+      code: `
+        class Foo {
+          readonly #privateField = 'foo';
+          #privateMember() {}
+        }
+        function foo(arg: Foo) {}
+      `,
+      options: [
+        {
+          treatMethodsAsReadonly: true,
+        },
+      ],
+    },
 
     // parameter properties should work fine
     {
diff --git a/packages/type-utils/src/propertyTypes.ts b/packages/type-utils/src/propertyTypes.ts
index 5e2f1054239..09e04b9049d 100644
--- a/packages/type-utils/src/propertyTypes.ts
+++ b/packages/type-utils/src/propertyTypes.ts
@@ -7,7 +7,7 @@ export function getTypeOfPropertyOfName(
   escapedName?: ts.__String,
 ): ts.Type | undefined {
   // Most names are directly usable in the checker and aren't different from escaped names
-  if (!escapedName || !name.startsWith('__')) {
+  if (!escapedName || !isSymbol(escapedName)) {
     return checker.getTypeOfPropertyOfType(type, name);
   }
 
@@ -34,3 +34,18 @@ export function getTypeOfPropertyOfType(
     property.getEscapedName(),
   );
 }
+
+// Symbolic names need to be specially handled because TS api is not sufficient for these cases.
+function isSymbol(escapedName: string): boolean {
+  return isKnownSymbol(escapedName) || isPrivateIdentifierSymbol(escapedName);
+}
+
+// case for escapedName: "__@foo@10", name: "__@foo@10"
+function isKnownSymbol(escapedName: string): boolean {
+  return escapedName.startsWith('__@');
+}
+
+// case for escapedName: "__#1@#foo", name: "#foo"
+function isPrivateIdentifierSymbol(escapedName: string): boolean {
+  return escapedName.startsWith('__#');
+}