Cook the elbow macaroni according to package directions. Drain and set aside.
In a large saucepan, melt butter over medium heat. Whisk in flour and cook for 1 minute.
Gradually add milk, whisking constantly until the mixture thickens.
Stir in the ranch seasoning, cheddar cheese, and mozzarella. Mix until smooth and melted.
Add the cooked pasta and shredded chicken. Stir well to coat everything in the cheesy sauce.
Season with salt and pepper. Serve hot and enjoy!