 John CarradineDr. Sigmund Walters | Dr. Sigmund Walters |
 Evelyn AnkersBeth Colman | Beth Colman |
 Milburn StoneFred Mason | Fred Mason |
 Lloyd CorriganJohn Whipple | John Whipple |
 Fay HelmNurse Strand | Nurse Strand |
 Martha VickersDorothy Colman | Dorothy Colman |
 AcquanettaPaula Dupree, the Ape Woman | Paula Dupree, the Ape Woman |
 Vince BarnettCurly | Curly |
 Paul FixGruen | Gruen |
 Fred AldrichRoustabout (uncredited) | Roustabout (uncredited) |
 Clyde BeattyFred Mason (in long shots) (archive footage / uncredited) | Fred Mason (in long shots) (archive footage / uncredited) |
 Turhan BeyEnd Narrator (voice)(uncredited) | End Narrator (voice)(uncredited) |
 Eddie BordenDock Spectator (uncredited) | Dock Spectator (uncredited) |
 Ray CorriganCheela the Gorilla (uncredited) | Cheela the Gorilla (uncredited) |
| RRussell CusterCurley (uncredited) | Curley (uncredited) |
 Fern EmmettBeth's Murdered Neighbor (uncredited) | Beth's Murdered Neighbor (uncredited) |
| VVirginia EngelsTrapeze Artist (uncredited) | Trapeze Artist (uncredited) |
| AAlexander GillWaiter (uncredited) | Waiter (uncredited) |
| GGus GlassmireCoroner (uncredited) | Coroner (uncredited) |
| JJoel GoodkindSmall Boy (uncredited) | Small Boy (uncredited) |
 William GouldSheriff (uncredited) | Sheriff (uncredited) |
| AAl HaskellAl (uncredited) | Al (uncredited) |
 Harry HolmanDock Ticket Office Clerk | Dock Ticket Office Clerk |
 Tom LondonShip's Captain (archive footage) | Ship's Captain (archive footage) |
 Charles McAvoyCop (uncredited) | Cop (uncredited) |
 Frank MitchellHandler (uncredited) | Handler (uncredited) |
 Charles MortonDock Worker (uncredited) | Dock Worker (uncredited) |
 Edward Peil Sr.Jake - Handler (uncredited) | Jake - Handler (uncredited) |
 Stanley PriceMan on Dock (uncredited) | Man on Dock (uncredited) |
 Joey RayAttendant (uncredited) | Attendant (uncredited) |
