Trailer
 | Jake Gyllenhaal as Robert Graysmith |
 | Mark Ruffalo as David Toschi |
 | Anthony Edwards as William Armstrong |
 | Robert Downey Jr. as Paul Avery |
 | Chloë Sevigny as Melanie |
 | Elias Koteas as Jack Mulanax |
 | John Carroll Lynch as Arthur Leigh Allen |
 | Brian Cox as Melvin Belli |
 | Dermot Mulroney as Martin Lee |
 | Charles Fleischer as Bob Vaughn |
 | Zach Grenier as Mel Nicolai |
 | Philip Baker Hall as Sherwood Morrill |
 | James Le Gros as George Bawart |
 | Donal Logue as Ken Narlow |
 | Richmond Arquette as Zodiac 1 / Zodiac 2 |
 | Bob Stephenson as Zodiac 3 |
 | John Lacy as Zodiac 4 |
 | Ed Setrakian as Al Hyman |
 | John Getz as Templeton Peck |
 | John Terry as Charles Thieriot |
 | Candy Clark as Carol Fisher |
 | June Diane Raphael as Mrs. Toschi |
 | Ciara Hughes as Darlene Ferrin |
 | Lee Norris as Young Mike Mageau |
 | Patrick Scott Lewis as Bryan Hartnell |
 | Pell James as Cecilia Shepard |
 | David Lee Smith as Father |
 | Jason Wiles as Lab Tech Dagitz |
 | Charles Schneider as Cabbie / Paul Stine |
 | James Carraway as Shorty |
 | Tom Verica as Jim Dunbar |
 | Jimmi Simpson as Mike Mageau |
 | Doan Ly as Belli's Housekeeper |
 | Karina Logue as Woman |
 | Joel Bissonnette as Inspector Kracke |
 | John Mahon as Riverside Captain |
 | Matt Winston as John Allen |
 | Jules Bruff as Catherine Allen |
 | John Ennis as Terry Pascoe |
 | J. Patrick McCormack as Police Commissioner |
 | Adam Goldberg as Duffy Jennings |
 | Clea DuVall as Linda del Buono |
 | Paul Schulze as Sandy Panzarella |
 | Adam Trese as Detective #1 |
 | Penny Wallace as Mulanax's Secretary |
 | John Hemphill as Donald Cheney |
 | Michel Francoeur as Man on Marquee |
 | Thomas Kopache as Copy Editor #1 |
 | Barry Livingston as Copy Editor #3 |
 | Christopher John Fields as Copy Editor #4 |
| Jack Samson as Young David Graysmith |
 | Micah Sauers as David Graysmith |
 | Zachary Sauers as Aaron Graysmith |
| Jessica Baltutis as Margot Graysmith |
 | Peter Quartaroli as Patrolman Fouke |
 | Geoff Callan as Patrolman Zelms |
| Michael Hungerford as Truck Driver |
 | Anna Katarina as Society Woman |
 | E.P. McKnight as Informant (Hall of Justice A) |
 | Betty Murphy as Informant |
 | Jeff Daniel Phillips as Informant |
 | Shane Woodson as Informant |
| Cookie Crawford as Informant #8 |
 | Cassius M. Willis as Uniform Cop |
 | Judith Drake as Florence Douglas |
 | Phoebe Holston as Prison Guard |
 | Marty Lodge as Pinole Foreman |
 | Cooper Thornton as Internal Affairs Agent #1 |
 | Cazimir Milostan as Internal Affairs Agent #2 |
| Charlotte Ferguson as Kathleen Johns' Baby |
| Phoebe Ferguson as Kathleen Johns' Baby |
| Kacey Malmsten as Kathleen Johns' Baby |
| Karly Malmsten as Kathleen Johns' Baby |
 | JD Cullum as Director |
 | Stanley B. Herman as Staff Editor |
 | Roy Lee Jones as Distraught African American Male |
 | Michael Rose as Navy Project Leader |
 | James Joseph O'Neil as DOD Project Leader |
 | Rod Damer as FBI Codebreaker |
| John Sarno as Donald Harden |
| Gloria Grant as Bettye Harden |
 | Brett Rickaby as Detective Roy |
| M.F. Bernier as Detective #2 |
| Carter Evans as Newscaster #2 |
 | Bill Seward as TV News Anchor |
| Dave Nemeth as Newscaster #4 |
 | Ted Garcia as Anchorman #1 |
| Greg Wolf as Interviewer #1 |
| Barry LeBrock as Reporter |
 | Ione Skye as Kathleen Johns (uncredited) |
| David Winston Barge as Vallejo Desk Ofiicer (uncredited) |
| Hayati Akbas as Hardware Store Customer (uncredited) |
 | Brad Carr as Camera Man (uncredited) |
| Mitchell Fink as Reporter (uncredited) |
| Erica Ford as Traveler (uncredited) |
| Tish Hicks as Informant (uncredited) |
 | Danielle McKee as Prisoner (uncredited) |
| Derris Nile as Office Worker (uncredited) |
| Carmen Plumb as Janie (uncredited) |
| Callie Thompson as Child Witness (uncredited) |
 | Bud Davis as Patrolman (uncredited) |
| Production | |
| Bradley J. Fischer | Producer |
| James Vanderbilt | Producer |
Art | |
| Donald Graham Burt | Production Design |
Production | |
| Arnold Messer | Producer |
Editing | |
| Angus Wall | Editor |
Sound | |
| David Shire | Original Music Composer |
Production | |
| Mike Medavoy | Producer |
| Ceán Chaffin | Producer |
Writing | |
| James Vanderbilt | Screenplay |
Camera | |
| Harris Savides | Director of Photography |
Directing | |
| David Fincher | Director |
Production | |
| Louis Phillips | Executive Producer |
Costume & Make-Up | |
| Casey Storm | Costume Design |
Sound | |
| George Drakoulias | Music Supervisor |
Costume & Make-Up | |
| Trish Almeida | Key Hair Stylist |
| Miia Kovero | Hairstylist |
| Kelvin R. Trahan | Hair Department Head |
| Felicity Bowring | Makeup Department Head |
Sound | |
| Randall Poster | Music Supervisor |
Costume & Make-Up | |
| Amy Schmiederer | Makeup Artist |
Sound | |
| Bryan Lawson | Music Editor |
Art | |
| Victor J. Zolfo | Set Decoration |
Production | |
| Laray Mayfield | Casting |
Sound | |
| David C. Hughes | Sound Effects Editor |
Production | |
| Daniel M. Stillman | Unit Production Manager |
Sound | |
| Michael Semanick | Sound Re-Recording Mixer |
| David Parker | Sound Re-Recording Mixer |
| Ren Klyce | Sound Designer |
Art | |
| Keith P. Cunningham | Art Direction |
Writing | |
| Robert Graysmith | Book |
Sound | |
| Richard Hymns | Supervising Sound Editor |
Crew | |
| Mickey Giacomazzi | Stunt Coordinator |
Costume & Make-Up | |
| Stacy Horn | Costume Supervisor |
Sound | |
| Martin Erskine | Music Editor |
Directing | |
| Kristine Kelly | Script Supervisor |
Camera | |
| Merrick Morton | Still Photographer |
Sound | |
| Addison Teague | Sound Effects Editor |
| Drew Kunin | Sound mixer |
| Jonathon Stevens | Music Editor |
Lighting | |
| John R. Manocchia | Rigging Gaffer |
Sound | |
| Ren Klyce | Supervising Sound Editor |
Directing | |
| Sally Sue Beisel | Second Assistant Director |
| Mary Ellen Woods | First Assistant Director |
Sound | |
| Richard Quinn | Dialogue Editor |
| Malcolm Fife | Dialogue Editor |
Crew | |
| Steve Hart | Stunts |
Visual Effects | |
| Glenn Cotter | 3D Artist |
| Edson Williams | Visual Effects Supervisor |
| Natalia de la Garza | Digital Compositor |
Crew | |
| Scotty Richards | Stunt Coordinator |
Visual Effects | |
| Eric Barba | Visual Effects Supervisor |
Lighting | |
| Isaac McKee | Lighting Technician |
