John Carradine
Role: Dr. Sigmund Walters
Evelyn Ankers
Role: Beth Colman
Milburn Stone
Role: Fred Mason
Lloyd Corrigan
Role: John Whipple
Fay Helm
Role: Nurse Strand
Martha Vickers
Role: Dorothy Colman
Acquanetta
Role: Paula Dupree, the Ape Woman
Fred Aldrich
Role: Roustabout (uncredited)
Clyde Beatty
Role: Fred Mason (in long shots) (archive footage / uncredited)
Turhan Bey
Role: End Narrator (voice)(uncredited)
Eddie Borden
Role: Dock Spectator (uncredited)
Ray Corrigan
Role: Cheela the Gorilla (uncredited)
Russell Custer
Role: Curley (uncredited)
Fern Emmett
Role: Beth's Murdered Neighbor (uncredited)
Virginia Engels
Role: Trapeze Artist (uncredited)
Alexander Gill
Role: Waiter (uncredited)
Gus Glassmire
Role: Coroner (uncredited)
Joel Goodkind
Role: Small Boy (uncredited)
William Gould
Role: Sheriff (uncredited)
Al Haskell
Role: Al (uncredited)
Harry Holman
Role: Dock Ticket Office Clerk
Tom London
Role: Ship's Captain (archive footage)
Charles McAvoy
Role: Cop (uncredited)
Frank Mitchell
Role: Handler (uncredited)
Charles Morton
Role: Dock Worker (uncredited)
Edward Peil Sr.
Role: Jake - Handler (uncredited)
Stanley Price
Role: Man on Dock (uncredited)
Joey Ray
Role: Attendant (uncredited)
Cap Somers
Role: Roustabout (uncredited)
Ray Walker
Role: Ringmaster (uncredited)
Anthony Warde
Role: Tony - Handler (uncredited)
Grant Withers
Role: Veterinarian (uncredited)
