Jake Gyllenhaal Robert Graysmith
Robert Downey Jr. Paul Avery
Mark Ruffalo David Toschi
Brian Cox Melvin Belli
Adam Goldberg Duffy Jennings
Dermot Mulroney Martin Lee
Jimmi Simpson Mike Mageau
James Le Gros George Bawart
Chloë Sevigny Melanie
Donal Logue Ken Narlow
John Carroll Lynch Arthur Leigh Allen
David Fincher Director
Elias Koteas Jack Mulanax
Anthony Edwards William Armstrong
Ione Skye Kathleen Johns (uncredited)
J. Patrick McCormack Police Commissioner
Clea DuVall Linda del Buono
Paul Schulze Sandy Panzarella
John Getz Templeton Peck
Zach Grenier Mel Nicolai
June Diane Raphael Mrs. Toschi
Philip Baker Hall Sherwood Morrill
Karina Logue Woman
Tom Verica Jim Dunbar
Christopher John Fields Copy Editor #4
Ceán Chaffin Producer
James Joseph O'Neil DOD Project Leader
David C. Hughes Sound Effects Editor
M.F. Bernier Detective #2
Dave Nemeth Newscaster #4
Jeff Daniel Phillips Informant
Daniel M. Stillman Unit Production Manager
Candy Clark Carol Fisher
Victor J. Zolfo Set Decoration
Merrick Morton Still Photographer
Kelvin R. Trahan Hair Department Head
Matt Winston John Allen
Michael Hungerford Truck Driver
Barry Livingston Copy Editor #3
Jason Wiles Lab Tech Dagitz
John R. Manocchia Rigging Gaffer
Richmond Arquette Zodiac 1 / Zodiac 2
James Vanderbilt Screenplay, Producer
Peter Quartaroli Patrolman Fouke
David Lee Smith Father
Charles Fleischer Bob Vaughn
John Lacy Zodiac 4
Brett Rickaby Detective Roy
Lee Norris Young Mike Mageau
Cassius M. Willis Uniform Cop
Keith P. Cunningham Art Direction
Michael Rose Navy Project Leader
Betty Murphy Informant
Ted Garcia Anchorman #1
David Winston Barge Vallejo Desk Ofiicer (uncredited)
Bob Stephenson Zodiac 3
Thomas Kopache Copy Editor #1
Judith Drake Florence Douglas
Sally Sue Beisel Second Assistant Director
Cazimir Milostan Internal Affairs Agent #2
Mickey Giacomazzi Stunt Coordinator
Scotty Richards Stunt Coordinator
Donald Graham Burt Production Design
John Terry Charles Thieriot
Randall Poster Music Supervisor
Adam Trese Detective #1
George Drakoulias Music Supervisor
Bud Davis Patrolman (uncredited)
Michael Semanick Sound Re-Recording Mixer
Steve Hart Stunts
Mary Ellen Woods First Assistant Director
David Parker Sound Re-Recording Mixer