Michael Rennie as Lord John Roxton

Jill St. John as Jennifer Holmes

David Hedison as Ed Malone

Claude Rains as Prof. George Edward Challenger

Fernando Lamas as Manuel Gomez

Richard Haydn as Prof. Summerlee

Ray Stricklyn as David Holmes

Jay Novello as Costa

Vitina Marcus as Native Girl

Ian Wolfe as Burton White

Colin Campbell as Prof. Waldron (uncredited)

John Graham as Stuart Holmes (uncredited)

Larry Chance as Indian Chief (uncredited)

Bert Stevens as Reporter at Airport (uncredited)

Al Bain as Man at Airport (uncredited)

Bess Flowers as Guest at Zoological Institute Forum (uncredited)

Kenner G. Kemp as Guest at Zoological Institute Forum (uncredited)

Cosmo Sardo as Guest at Zoological Institute Forum (uncredited)

Murray Pollack as Guest at Zoological Institute Forum (uncredited)