Alderton is a census-designated place (CDP) in Pierce County, Washington, United States. The population was 2,893 at the 2010 census. The community is located in the Puyallup River Valley between the cities of Sumner and Orting.
Alderton is located at 47°10′10″N 122°13′45″W / 47.16944°N 122.22917°W / 47.16944; -122.22917 (47.169444, -122.229167).
According to the United States Census Bureau, the CDP has a total area of 5.46 square miles (8.4 km²), of which, 5.32 square miles (8.3 km²) of it is land and 0.14 square miles (0.08 km²) of it (2.55%) is water.