Jake Gyllenhaal Robert Graysmith
Robert Downey Jr. Paul Avery
Mark Ruffalo David Toschi
Dermot Mulroney Martin Lee
Brian Cox Melvin Belli
Anthony Edwards William Armstrong
Jimmi Simpson Mike Mageau
David Fincher Director
Donal Logue Ken Narlow
Chloë Sevigny Melanie
John Carroll Lynch Arthur Leigh Allen
Elias Koteas Jack Mulanax
Clea DuVall Linda del Buono
Adam Goldberg Duffy Jennings
Philip Baker Hall Sherwood Morrill
John Getz Templeton Peck
Tom Verica Jim Dunbar
Ione Skye Kathleen Johns (uncredited)
Paul Schulze Sandy Panzarella
Zach Grenier Mel Nicolai
June Diane Raphael Mrs. Toschi
James Vanderbilt Screenplay, Producer
Jason Wiles Lab Tech Dagitz
David Lee Smith Father
James Le Gros George Bawart
Candy Clark Carol Fisher
Lee Norris Young Mike Mageau
Richmond Arquette Zodiac 1 / Zodiac 2
Judith Drake Florence Douglas
Karina Logue Woman
John Lacy Zodiac 4
Thomas Kopache Copy Editor #1
Charles Fleischer Bob Vaughn
Barry Livingston Copy Editor #3
Bob Stephenson Zodiac 3
John Terry Charles Thieriot
Christopher John Fields Copy Editor #4
Joel Bissonnette Inspector Kracke
Matt Winston John Allen
Jeff Daniel Phillips Informant
J. Patrick McCormack Police Commissioner
Michael Semanick Sound Re-Recording Mixer
Roy Lee Jones Distraught African American Male
John Ennis Terry Pascoe
Cooper Thornton Internal Affairs Agent #1
Mickey Giacomazzi Stunt Coordinator
Michael Rose Navy Project Leader
George Drakoulias Music Supervisor
John R. Manocchia Rigging Gaffer
Brett Rickaby Detective Roy
JD Cullum Director
Daniel M. Stillman Unit Production Manager
Pell James Cecilia Shepard
Adam Trese Detective #1
Anna Katarina Society Woman
Angus Wall Editor
Ceán Chaffin Producer
David C. Hughes Sound Effects Editor
Ciara Hughes Darlene Ferrin
Drew Kunin Sound mixer
Ren Klyce Supervising Sound Editor, Sound Designer
Donald Graham Burt Production Design
Betty Murphy Informant
Cazimir Milostan Internal Affairs Agent #2
Bradley J. Fischer Producer
Richard Hymns Supervising Sound Editor
John Mahon Riverside Captain
Mike Medavoy Producer
Stanley B. Herman Staff Editor
Edson Williams Visual Effects Supervisor
Cassius M. Willis Uniform Cop
Harris Savides Director of Photography