- Buster Crabbe
- Buck Rogers
- Constance Moore
- Wilma Deering
- Jackie Moran
- George 'Buddy' Wade
- Jack Mulhall
- Captain Rankin
- Anthony Warde
- Killer Kane
- Philson Ahn
- Prince Tallen
- C. Montague Shaw
- Doctor Huer
- Guy Usher
- Aldar
- William Gould
- Air Marshal Kragg
- Henry Brandon
- Captain Laska
- Wheeler Oakman
- Lieutenant Patten
- Kenne Duncan
- Lieutenant Lacy
- Carleton Young
- Scott
- Reed Howes
- Captain Roberts
- Wade Boteler
- Professor Wade
- Al Bridge
- Dynamo Room Floor Guard
- Roy Butler
- Control Officer
- Eddy Chandler
- Braeden - Captain of Dirigible [Ch. 1]
- Lane Chandler
- Army Official at Wade's Lab
- Russ Clark
- Lieutenant Carson [Chs. 10-11]
- James Conaty
- Kane's Councilman
- Cyril Delevanti
- Saturnian Councilman
- Frank Ellis
- Kane's Soldier
- Jack Gardner
- Professor Huer's Lab Assistant
- Karl Hackett
- Councillor Krenko
- Kenneth Harlan
- Reporter at Wade's Lab
- John Harmon
- Hidden City Air Controller
- Ben Lewis
- Cell Guard [Ch. 10]
- Theodore Lorch
- Kane's Council Member
- Edmund Mortimer
- Member of War Council [Ch. 12]
- Eddie Parker
- Council Room Guard
- Stanley Price
- Captain Martin / Zugg Man (uncredited)
- Francis Sayles
- Saturnian Councilman
- David Sharpe
- Kane's Pilot / Hidden City Sentry / Saturnian Lieutenant (uncredited)
- Tom Steele
- Kane's Pilot / Hidden City Tech / Balcony Guard (uncredited)
- Phillip Trent
- Mitchell [Ch. 1]
