Chesterbrook is a census-designated place in Chester County, Pennsylvania, United States. It is located within the Philadelphia metropolitan area and just south of Valley Forge National Historical Park. The population was 4,589 at the 2010 census. Chesterbrook is a development located in Tredyffrin Township which is located in Chester County. It is not a town, unincorporated or otherwise. It is in the Chester County side of Wayne.