Yardley is a borough in Bucks County, Pennsylvania, United States. Yardley borders the Delaware River and Ewing, New Jersey to its east and Lower Makefield Township to its north, west, and south. The United States Post Office assigns many addresses in Lower Makefield Township the preferred city of "Yardley", although they are outside the borough. The population was 2,434 at the 2010 census. Yardley is part of the Delaware Valley metropolitan area.