Centereach is a hamlet and census-designated place in Suffolk County, New York, United States. The population was 31,578 at the 2010 census. The hamlet of Centereach was first called West Middle Island, but primarily became known as New Village until the early 20th century. When it was discovered that another village shared the same name, the name wa…Centereach is a hamlet and census-designated place in Suffolk County, New York, United States. The population was 31,578 at the 2010 census. The hamlet of Centereach was first called West Middle Island, but primarily became known as New Village until the early 20th century. When it was discovered that another village shared the same name, the name was changed to Centereach in 1916. The name Centereach reflects the centrality of the hamlet's location on Long Island, literally meaning "center reached".