- Michael Rennie
- Lord John Roxton
- Jill St. John
- Jennifer Holmes
- David Hedison
- Ed Malone
- Claude Rains
- Prof. George Edward Challenger
- Fernando Lamas
- Manuel Gomez
- Richard Haydn
- Prof. Summerlee
- Ray Stricklyn
- David Holmes
- Jay Novello
- Costa
- Vitina Marcus
- Native Girl
- Ian Wolfe
- Burton White
- Al Bain
- Man at Airport
- Ross Brown
- Airport Attendant
- Colin Campbell
- Prof. Waldron
- Fred Cavens
- French Member of Zoological Institute Forum
- Larry Chance
- Indian Chief
- Phyllis Coghlan
- British Member of Zoological Institute Forum
- Paul Cristo
- Guest at Zoological Institute Forum
- Anne Dore
- Member of Zoological Institute Forum
- Alex Finlayson
- Reporter
- Bess Flowers
- Guest at Zoological Institute Forum
- Charles Fogel
- Guest at Zoological Institute Forum
- Peter Fontaine
- Airport Attendant
- Don Forbes
- TV Announcer
- John Graham
- Stuart Holmes
- Sam Harris
- Man at Airport / Guest at Zoological Institute Forum (uncredited)
- Ivo Henderson
- British Member of Zoological Institute Forum
- George Holmes
- Guest at Zoological Institute Forum
- Stuart Holmes
- Zoological Institute Professor on Stage
- Freda Jones
- Guest at Zoological Institute Forum
- Kenner G. Kemp
- Guest at Zoological Institute Forum
- Harold Miller
- Guest at Zoological Institute Forum
- Sándor Naszódy
- German Member of Zoological Institute Forum
- George Pelling
- Reporter
- Murray Pollack
- Guest at Zoological Institute Forum
- Ruggero Romor
- Italian Member of Zoological Institute Forum
- Brian Roper
- British Member of Zoological Institute Forum
- Cosmo Sardo
- Guest at Zoological Institute Form
- Owen Song
- Guest at Zoological Institute Forum
- Jacqueline Squire
- British Member of Zoological Institute Forum
- Bert Stevens
- Reporter at Airport
- Gilchrist Stuart
- Reporter
- Ben Wright
- BBC Field Reporter Ted Bottomley
