Pacheco is a census-designated place (CDP) in Contra Costa County, California, United States. The population was 3,685 at the 2010 census. It is located 5.5 miles (9 km) north of Walnut Creek.
According to the United States Census Bureau, the CDP has a total area of 0.7 square miles (1.9 km²), all of it land.
The town was laid out in 1857 by Dr. J.H. Carothers and named for Salvio Pacheco, grantee of the Rancho Monte del Diablo Mexican land grant. A post office operated at Pacheco from 1859 to 1913 and from 1955 to the present.