Hedy Lamarr
— Tondelayo
Walter Pidgeon
— Mr. Harry Witzel
Frank Morgan
— The Doctor
Richard Carlson
— Mr. Langford
Reginald Owen
— Skipper of the Congo Queen
Henry O'Neill
— The Reverend Dr. Roberts
Bramwell Fletcher
— Wilbur Ashley
Clyde Cook
— Ted, First Mate of the Congo Queen
Leigh Whipper
— Jim Fish
Oscar Polk
— Umeela
Darby Jones
— Darby
Richard Ainley
— Mr. Worthing
Jim Davis
— Seaplane Pilot (uncredited)
John Burton
— Jim Benson (uncredited)
Delos Jewkes
— Native Singer (uncredited)
Martin Wilkins
— Native Prisoner (uncredited)
Ed Allen
— Native Drug Seller (uncredited)