- Buster Crabbe
- Flash Gordon
- Jean Rogers
- Dale Arden
- Charles Middleton
- Ming the Merciless
- Priscilla Lawson
- Princess Aura
- Frank Shannon
- Dr. Alexis Zarkov
- Richard Alexander
- Prince Barin [Chs. 5-13]
- Jack 'Tiny' Lipson
- King Vultan [Chs. 5-13]
- Theodore Lorch
- High Priest #2 [Chs. 8-11, 13]
- Richard Tucker
- Professor Gordon
- George Cleveland
- Professor Hensley
- James Pierce
- Prince Thun [Chs. 2-9, 12-13]
- Duke York
- King Kala [Chs. 2-5]
- Muriel Goodspeed
- Zona [Ch. 4]
- Earl Askam
- Officer Torch
- House Peters Jr.
- Shark Man [Chs. 3-4]
- John Bagni
- Hawkman Throne Room Guard
- Roy Barcroft
- Throne Guard
- Carroll Borland
- Woman in Ming's Palace
- Lynton Brent
- Transcontinental Plane Steward
- Don Brodie
- Earth Radio Scientist
- Lane Chandler
- Sharkman / Ming's Soldier (uncredited)
- Howard Christie
- Shark Man
- Jim Corey
- Shark Man
- Ray Corrigan
- Orangopoid
- William Desmond
- Hawkman Lookout Captain
- Al Ferguson
- Spaceograph Operator
- Jerry Frank
- Shark Man
- Sig Frohlich
- Shark Man
- Saul A. Goodkind
- (voice) (uncredited)
- Olive Hatch
- Aura's Handmaiden
- Reed Howes
- Airplane Pilot
- Fred Kohler Jr.
- Robot / Ming's Soldier (uncredited)
- George Magrill
- Ming's Soldier
- Charles McMurphy
- Atom Furnace Slavedriver
- Monte Montague
- Ming's Soldier
- Bull Montana
- Monkey Man
- Eddie Parker
- Ming's Soldier
- Lon Poff
- High Priest #1
- Sana Rayya
- Priestess of Tigron
- Constantine Romanoff
- Monkey Man
- Fred Scott
- Soldier with Drugged Wine
- Cap Somers
- Shark Man
- Tom Steele
- Plane Passenger
- Glenn Strange
- Robot / Ming's Soldier / Gocko (uncredited)
- Bunny Waters
- Shark Man
- Slim Whitaker
- Prison Guard
- Harry Wilson
- Pit Control Operator
