- Jake Gyllenhaal as Louis "Lou" Bloom[5]
- Rene Russo as Nina Romina[5]
- Riz Ahmed as Rick[5]
- Bill Paxton as Joe Loder[5]
- Kevin Rahm as Frank Kruse[5]
- Michael Hyatt as Detective Frontieri[5]
- Ann Cusack as Linda
Carolyn Gilroy, the daughter of editor John Gilroy and niece of director Dan Gilroy, portrays KWLA 6 employee Jenny. Michael Papajohn, James Huang, Eric Lange, Kiff VandenHeuvel, Myra Turley, and Jamie McShane play a security guard, Joe's video assistant, a cameraman, a news editor, a neighbor, and a motorist, respectively. Detective Lieberman, Frontieri's partner, is portrayed by Price Carson. Journalists Kent Shocknek, Pat Harvey, Sharon Tay, Rick Garcia, and Bill Seward appear as themselves.