Ruben Fleischer's (Zombieland) 1940s-set crime drama stars Penn as real-life gangster Mickey Cohen, who was personally targeted by the LAPD special task force referenced in the title.
Nick Nolte, Anthony Mackie, Giovanni Ribisi and Michael Peña are among the supporting cast.
Gangster Squad's release date was pushed back this summer following the cinema shooting in Aurora, Colorado.
This was owing to a scene in which mobsters open fire on cinemagoers in Grauman's Chinese Theatre on Hollywood Boulevard, which has since been reshot.
Gangster Squad will open on January 11.
Watch the trailer below: