Boris Karloff as Dr. Bernard Adrian

Maris Wrixon as Frances Clifford

Gene O'Donnell as Danny Foster

Dorothy Vaughan as Mother Clifford

Henry Hall as Sheriff Jeff Halliday

Selmer Jackson as Dr. McNulty

Gertrude Hoffmann as Jane the Housekeeper

Jessie Arnold as Mrs. Brill

Billy Bletcher as Short Mustached Posse Man

Harry C. Bradley as Quinn

George Cleveland as Mr. Howley

Ray Corrigan as Nabu

Pauline Drake as Young Girl

Mary Field as Mrs. Mason

Gibson Gowland as Posse Member

Julia Griffith as Townswoman

I. Stanford Jolley as Ape Trainer

Stan Jolley as Boy in Soda Shop

Jack Kennedy as Dep. Archie Tomlin

Donald Kerr as Citizen Carrying Mauled Ape Trainer

Philo McCullough as Henry Mason

Buddy Swan as Willie Brill

Minerva Urecal as Townswoman