Old Tappan ( ) is a borough in Bergen County, New Jersey, United States. As of the 2010 United States Census, the borough's population was 5,750, reflecting an increase of 268 (+4.9%) from the 5,482 counted in the 2000 Census, which had in turn increased by 1,228 (+28.9%) from the 4,254 counted in the 1990 Census.