Harrington Park is a borough in Bergen County, in the U.S. state of New Jersey. As of the 2020 United States census, the borough's population was 4,741, an increase of 77 from the 2010 census count of 4,664, which in turn reflected a decrease of 76 from the 4,740 counted in the 2000 census. Harrington Park was formed on March 29, 1904, from portions of Harrington Township and Washington Township, and parts of the borough of Closter.