Jake Gyllenhaal

Character: Robert Graysmith

Mark Ruffalo

Character: David Toschi

Anthony Edwards

Character: William Armstrong

Robert Downey Jr.

Character: Paul Avery

Chloë Sevigny

Character: Melanie

Elias Koteas

Character: Jack Mulanax

John Carroll Lynch

Character: Arthur Leigh Allen

Brian Cox

Character: Melvin Belli

Dermot Mulroney

Character: Martin Lee

Charles Fleischer

Character: Bob Vaughn

Zach Grenier

Character: Mel Nicolai

Philip Baker Hall

Character: Sherwood Morrill

James LeGros

Character: George Bawart

Donal Logue

Character: Ken Narlow

Richmond Arquette

Character: Zodiac 1 / Zodiac 2

Bob Stephenson

Character: Zodiac 3

John Lacy

Character: Zodiac 4

Ed Setrakian

Character: Al Hyman

John Getz

Character: Templeton Peck

John Terry

Character: Charles Thieriot

Candy Clark

Character: Carol Fisher

June Diane Raphael

Character: Mrs. Toschi

Ciara Hughes

Character: Darlene Ferrin

Lee Norris

Character: Young Mike Mageau

Patrick Scott Lewis

Character: Bryan Hartnell

Pell James

Character: Cecilia Shepard

David Lee Smith

Character: Father

Jason Wiles

Character: Lab Tech Dagitz

Charles Schneider

Character: Cabbie / Paul Stine

James Carraway

Character: Shorty

Tom Verica

Character: Jim Dunbar

Jimmi Simpson

Character: Mike Mageau

Doan Ly

Character: Belli's Housekeeper

Karina Logue

Character: Woman

Joel Bissonnette

Character: Inspector Kracke

John Mahon

Character: Riverside Captain

Matt Winston

Character: John Allen

Jules Bruff

Character: Catherine Allen

John Ennis

Character: Terry Pascoe

J. Patrick McCormack

Character: Police Commissioner

Adam Goldberg

Character: Duffy Jennings

Clea DuVall

Character: Linda del Buono

Paul Schulze

Character: Sandy Panzarella

Adam Trese

Character: Detective #1

Penny Wallace

Character: Mulanax's Secretary

John Hemphill

Character: Donald Cheney

Michel Francoeur

Character: Man on Marquee

Thomas Kopache

Character: Copy Editor #1

Barry Livingston

Character: Copy Editor #3

Christopher John Fields

Character: Copy Editor #4

Jack Samson

Character: Young David Graysmith

Micah Sauers

Character: David Graysmith

Zachary Sauers

Character: Aaron Graysmith

Jessica Baltutis

Character: Margot Graysmith

Peter Quartaroli

Character: Patrolman Fouke

Geoff Callan

Character: Patrolman Zelms

Michael Hungerford

Character: Truck Driver

Anna Katarina

Character: Society Woman

E.P. McKnight

Character: Informant (Hall of Justice A)

Betty Murphy

Character: Informant

Jeff Daniel Phillips

Character: Informant

Shane Woodson

Character: Informant

Cookie Crawford

Character: Informant #8

Cassius M. Willis

Character: Uniform Cop

Judith Drake

Character: Florence Douglas

Phoebe Holston

Character: Prison Guard

Marty Lodge

Character: Pinole Foreman

Cooper Thornton

Character: Internal Affairs Agent #1

Cazimir Milostan

Character: Internal Affairs Agent #2

Charlotte Ferguson

Character: Kathleen Johns' Baby

Phoebe Ferguson

Character: Kathleen Johns' Baby

Kacey Malmsten

Character: Kathleen Johns' Baby

Karly Malmsten

Character: Kathleen Johns' Baby

JD Cullum

Character: Director

Stanley B. Herman

Character: Staff Editor

Roy Lee Jones

Character: Distraught African American Male

Michael Rose

Character: Navy Project Leader

James Joseph O'Neil

Character: DOD Project Leader

Rod Damer

Character: FBI Codebreaker

John Sarno

Character: Donald Harden

Gloria Grant

Character: Bettye Harden

Brett Rickaby

Character: Detective Roy

M.F. Bernier

Character: Detective #2

Carter Evans

Character: Newscaster #2

Bill Seward

Character: TV News Anchor

Dave Nemeth

Character: Newscaster #4

Ted Garcia

Character: Anchorman #1

Greg Wolf

Character: Interviewer #1

Barry LeBrock

Character: Reporter

Ione Skye

Character: Kathleen Johns (uncredited)

David Winston Barge

Character: Vallejo Desk Ofiicer (uncredited)

Hayati Akbas

Character: Hardware Store Customer (uncredited)

Brad Carr

Character: Camera Man (uncredited)

Mitchell Fink

Character: Reporter (uncredited)

Erica Ford

Character: Traveler (uncredited)

Tish Hicks

Character: Informant (uncredited)

Danielle McKee

Character: Prisoner (uncredited)

Derris Nile

Character: Office Worker (uncredited)

Carmen Plumb

Character: Janie (uncredited)

Callie Thompson

Character: Child Witness (uncredited)

Bud Davis

Character: Patrolman (uncredited)