The three actors join Kristen Wiig, Melissa McCarthy, Leslie Jones and Kate McKinnon in the Paul Feig-directed movie, reported TheWrap.
Andy Garcia has signed up to play the Mayor of New York City.
Although the film is currently shooting in Boston, it will be set in New York City.
Williams, known for his role Omar on HBO's series "The Wire", is set to play a character named Hawkins.
There is no detail yet about the role Strong will portray.