Jake Gyllenhaal Robert Graysmith
Robert Downey Jr. Paul Avery
Mark Ruffalo David Toschi
Dermot Mulroney Martin Lee
Brian Cox Melvin Belli
Chloë Sevigny Melanie
Anthony Edwards William Armstrong
Jimmi Simpson Mike Mageau
David Fincher Director
Donal Logue Ken Narlow
Elias Koteas Jack Mulanax
John Carroll Lynch Arthur Leigh Allen
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
Karina Logue Woman
John Lacy Zodiac 4
Barry Livingston Copy Editor #3
Judith Drake Florence Douglas
Charles Fleischer Bob Vaughn
John Terry Charles Thieriot
Christopher John Fields Copy Editor #4
Joel Bissonnette Inspector Kracke
Thomas Kopache Copy Editor #1
Matt Winston John Allen
Jeff Daniel Phillips Informant
Bob Stephenson Zodiac 3
Michael Semanick Sound Re-Recording Mixer
Roy Lee Jones Distraught African American Male
J. Patrick McCormack Police Commissioner
John Ennis Terry Pascoe
Cooper Thornton Internal Affairs Agent #1
Mickey Giacomazzi Stunt Coordinator
Donald Graham Burt Production Design
Michael Rose Navy Project Leader
George Drakoulias Music Supervisor
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
Ceán Chaffin Producer
David C. Hughes Sound Effects Editor
Ciara Hughes Darlene Ferrin
Drew Kunin Sound mixer
Ren Klyce Supervising Sound Editor, Sound Designer
Betty Murphy Informant
Cazimir Milostan Internal Affairs Agent #2
John Mahon Riverside Captain
Mike Medavoy Producer
Edson Williams Visual Effects Supervisor
Cassius M. Willis Uniform Cop
Richard Hymns Supervising Sound Editor
Kelvin R. Trahan Hair Department Head
Harris Savides Director of Photography
Victor J. Zolfo Set Decoration
John R. Manocchia Rigging Gaffer
Keith P. Cunningham Art Direction