 Michael RennieLord John Roxton | Lord John Roxton |
 Jill St. JohnJennifer Holmes | Jennifer Holmes |
 David HedisonEd Malone | Ed Malone |
 Claude RainsProf. George Edward Challenger | Prof. George Edward Challenger |
 Fernando LamasManuel Gomez | Manuel Gomez |
 Richard HaydnProf. Summerlee | Prof. Summerlee |
 Ray StricklynDavid Holmes | David Holmes |
 Jay NovelloCosta | Costa |
 Vitina MarcusNative Girl | Native Girl |
 Ian WolfeBurton White | Burton White |
 Colin CampbellProf. Waldron (uncredited) | Prof. Waldron (uncredited) |
| JJohn GrahamStuart Holmes (uncredited) | Stuart Holmes (uncredited) |
 Larry ChanceIndian Chief (uncredited) | Indian Chief (uncredited) |
| BBert StevensReporter at Airport (uncredited) | Reporter at Airport (uncredited) |
 Al BainMan at Airport (uncredited) | Man at Airport (uncredited) |
 Bess FlowersGuest at Zoological Institute Forum (uncredited) | Guest at Zoological Institute Forum (uncredited) |
 Kenner G. KempGuest at Zoological Institute Forum (uncredited) | Guest at Zoological Institute Forum (uncredited) |
 Cosmo SardoGuest at Zoological Institute Forum (uncredited) | Guest at Zoological Institute Forum (uncredited) |
| MMurray PollackGuest at Zoological Institute Forum (uncredited) | Guest at Zoological Institute Forum (uncredited) |
