Dalton Trumbo

Cleo Trumbo

Hedda Hopper

Nikola Trumbo

Arlen Hird

Frank King

Edward G. Robinson

John Wayne

Buddy Ross

Edward 'Ed' Muhl

Sam Wood

Ian McLellan Hunter

J. Parnell Thomas

Louis B. Mayer

Virgil Brooks

Hymie King

Chris Trumbo (Age 13-17)

Kirk Douglas

Andrew Hird

Otto Preminger

Roy Brewer

Chris Trumbo (age 6-10) (as Tobias McDowell Nichols)

Himself (archive footage)

Party Goer

Niki Trumbo (age 8-11)

Robert Stripling

Reporter

Reporter

Robert Kenny

Jury Foreman

Jeff Krandall

Mitzi Trumbo (age 6-8)

Mitzi Trumbo (age 9-12)

Starlet (uncredited)

Ethel (uncredited)

Showgirl (uncredited)

Trumbo Friend (uncredited)

Showgirl (uncredited)

Juror (uncredited)

Irving Radovich in Roman Holiday (archive footage) (uncredited)

Self (archive footage) (uncredited)

Self (voice) (archive footage) (uncredited)

Self (archive footage) (uncredited)

Self (archive footage) (uncredited)

Crassus (archive footage) (uncredited)

Varinia (archive footage) (uncredited)

Self (archive footage) (uncredited)