Cedar Crest is a census-designated place (CDP) in the town of Marshfield, Plymouth County, Massachusetts, United States. It is named for a hill on the north side of Careswell Street. It is bordered to the south by the town of Duxbury and to the southeast by the community of Green Harbor. Cedar Crest was first listed as a CDP prior to the 2020 census. At the 2010 census, Cedar Crest and neighboring Green Harbor were part of a single CDP known as Green Harbor-Cedar Crest.