Elle Fanning Niki Trumbo
Audrey Hepburn Princess Ann (archive footage) (uncredited)
John Goodman Frank King
Bryan Cranston Dalton Trumbo
Helen Mirren Hedda Hopper
Diane Lane Cleo Trumbo
Stephen Root Hymie King
Lucille Ball Self (archive footage) (voice) (uncredited)
Alan Tudyk Ian McLellan Hunter
Eddie Albert Irving Radovich in Roman Holiday (archive footage) (uncredited)
Madison Wolfe Niki Trumbo (age 8-11)
Michael Stuhlbarg Edward G. Robinson
Jean Simmons Varinia (archive footage) (uncredited)
Deborah Kerr Self (archive footage) (uncredited)
Cary Grant Self (archive footage) (uncredited)
Robert Taylor Self (archive footage) (uncredited)
Danny Kaye Self (archive footage) (uncredited)
James Garner Self (archive footage) (uncredited)
Christian Berkel Otto Preminger
Adewale Akinnuoye-Agbaje Virgil Brooks
Louis C.K. Arlen Hird
Jay Roach Director, Producer
John Getz Sam Wood
Laurence Olivier Crassus (archive footage) (uncredited)
Gregory Peck Joe Bradley (archive footage) (uncredited)
Richard Portnow Louis B. Mayer
Ronald Reagan Self (archive footage) (uncredited)
Mark Harelik Ed Muhl, Edward 'Ed' Muhl
Dalton Trumbo Himself (archive footage)
Dan Bakkedahl Roy Brewer
Lauren Bacall Self (archive footage) (uncredited)
Dean O'Gorman Kirk Douglas
Sean Bridgers Jeff Krandall
James DuMont J. Parnell Thomas
Gary Archer Prosthetics
Roger Bart Buddy Ross
Geoffrey Haley "A" Camera Operator, Steadicam Operator
Peter MacKenzie Robert Kenny
David Rubin Casting
Johnny Sneed Robert Stripling
Janice Williams Producer
Jim Denault Director of Photography
Dane Rhodes Reporter
Garrett Hines Andrew Hird
Michael London Producer
David James Elliott John Wayne
John Neisler Jury Foreman
Theodore Shapiro Original Music Composer
Toby Nichols Chris Trumbo (age 6-10) (as Tobias McDowell Nichols)
Rio Hackford Reporter
Meghan Wolfe Mitzi Trumbo (age 6-8)
John McNamara Screenplay, Producer
Mattie Liptak Chris Trumbo (Age 13-17)
Jaclyn Bethany Starlet (uncredited)
Heather Arthur Stunt Coordinator
Alan Baumgarten Editor
Monica Levinson Producer, Unit Production Manager
Shivani Rawat Producer
Laura Flannery Party Goer
Cindy Carr Set Decoration
Jesse Rosenthal Art Direction
Michelle Graham Co-Producer
Daniel Orlandi Costume Designer
Jeri Habberstad Stunt Double
George Parra First Assistant Director
Mark Ricker Production Design
Kevin Kelly Brown Producer
Veronica Parks Showgirl (uncredited)
Suzanne LaChasse Showgirl (uncredited)
Scott August Second Assistant Director
Anne Speed Juror (uncredited)
Rhonda Laizer Trumbo Friend (uncredited)