The drama, which chronicles The Boston Globe's investigation into child abuse in the Catholic Church, features an all-star ensemble cast including Rachel McAdams and Michael Keaton.
Top acting honours went to Michael B Jordan for Rocky spin-off Creed and Charlotte Rampling for 45 Years.
Asif Kapadia's Amy Winehouse documentary won best non-fiction film.
Former Twilight star Kristen Stewart won best supporting actress for Clouds of Sils Maria, with British star Mark Rylance named best supporting actor for Bridge of Spies.
Best director went to Todd Haynes for Carol, which also picked up best cinematography for Ed Lachman.
Spotlight also won best screenplay for Josh Singer and Tom McCarthy.
Timbuktu, by Mauritanian director Abderrahmane Sissako, won best foreign language film.
Society members announced the winners at the Lincoln Centre for the Performing Arts in New York on Sunday.
Spotlight's success follows its win for best film at the Los Angeles Film Critics Association awards last month. It has also been nominated for a Golden Globe for best picture.
Creed was recently voted the best film of 2015 by the Black Film Critics Circle, where Jordan and Sylvester Stallone were named best actor and best supporting actor.
The US National Society of Film Critics has named Spotlight the best film of 2015.