diff --git a/crates/oxc_isolated_declarations/src/class.rs b/crates/oxc_isolated_declarations/src/class.rs
index 6d953758f72b6..bb38254fdfbf6 100644
--- a/crates/oxc_isolated_declarations/src/class.rs
+++ b/crates/oxc_isolated_declarations/src/class.rs
@@ -241,8 +241,12 @@ impl<'a> IsolatedDeclarations<'a> {
         let mut elements = self.ast.new_vec();
         for (index, param) in function.params.items.iter().enumerate() {
             if param.accessibility.is_some() || param.readonly {
-                // transformed params will definitely have type annotation
-                let type_annotation = self.ast.copy(&params.items[index].pattern.type_annotation);
+                let type_annotation = if param.accessibility.is_some_and(|a| a.is_private()) {
+                    None
+                } else {
+                    // transformed params will definitely have type annotation
+                    self.ast.copy(&params.items[index].pattern.type_annotation)
+                };
                 if let Some(new_element) =
                     self.transform_formal_parameter_to_class_property(param, type_annotation)
                 {
diff --git a/crates/oxc_isolated_declarations/tests/snapshots/class.snap b/crates/oxc_isolated_declarations/tests/snapshots/class.snap
index 2101b8b656efc..7baebea6d6077 100644
--- a/crates/oxc_isolated_declarations/tests/snapshots/class.snap
+++ b/crates/oxc_isolated_declarations/tests/snapshots/class.snap
@@ -29,7 +29,7 @@ export declare class Baz {
 }
 export declare class Boo {
 	readonly prop: number;
-	private readonly prop2: number;
+	private readonly prop2;
 	readonly prop3: number;
 	constructor(prop?: number, prop2?: number, prop3?: number);
 }