- Lionel Barrymore
- Count Andre Dakkar
- Jacqueline Gadsdon
- Countess Sonia Dakkar
- Lloyd Hughes
- Nikolai Roget
- Montagu Love
- Baron Falon
- Harry Gribbon
- Mikhail
- Snitz Edwards
- Anton
- Gibson Gowland
- Dmitry
- Dolores Brinkman
- Teresa
- Karl Dane
- Crewman
- Edward Connelly
- Radio Technician
- Robert Dudley
- Workman
- Sydney Jarvis
- Cossack
- Bob Kortman
- Island Stronghold Guard
- Robert McKim
- Captain of the Guard
- Angelo Rossitto
- Underwater Creature
- Carl 'Major' Roup
- Underwater Creature
- Sam Savitsky
- Crewman
- Billy Schuler
- Undetermined Secondary Role
- Evelyn Selbie
- Faithful Servant
- Jack Stoutenburg
- Undetermined Secondary Role
- Harry Tenbrook
- Radio Technician
