Mercerville is an unincorporated community and census-designated place located within Hamilton Township, in Mercer County, in the U.S. state of New Jersey. As of the 2020 census, the CDP's population was 13,447. Until after the 2000 census, the area was part of the Mercerville-Hamilton Square CDP. For the 2010 Census it was split into two CDPs, Mercerville and Hamilton Square.