East Greenbush is a census-designated place (CDP) in Rensselaer County, New York, United States. The population was 4,487 at the 2010 census. East Greenbush is mostly within the southern part of the town of East Greenbush, but a small section of the community extends southward into the town of Schodack. U.S. Routes 9 and 20 pass through the community, and the western end of U.S. Route 4 begins immediately north of the community.