Teaneck is a township in Bergen County, in the U.S. state of New Jersey. It is a bedroom community in the New York metropolitan area. As of the 2020 United States census, the township's population was 41,246, an increase of 1,470 (+3.7%) from the 2010 census count of 39,776, which in turn reflected an increase of 516 (+1.3%) from the 39,260 counted in the 2000 census. As of 2020, Teaneck was the second-most populous among the 70 municipalities in Bergen County, behind Hackensack, which had a population of 46,030.

Bergen County is the most populous county in the U.S. state of New Jersey. As of the 2020 United States census, the county's population was 955,732, its highest decennial count ever and an increase of 50,616 (+5.6%) from the 905,116 recorded at the 2010 census, which in turn reflected an increase of 20,998 (2.4%) from the 884,118 counted in the 2000 census. Located in the northeastern corner of New Jersey and its Gateway Region, Bergen County and its many inner suburbs constitute a highly developed part of the New York City metropolitan area, bordering the Hudson River; the George Washington Bridge, which crosses the Hudson, connects Bergen County with Manhattan. The county is part of the North Jersey region of the state.