Professor Bernard Quatermass
Detective Lomax
John Paterson
Doctor Gordon Briscoe
Judith Carroon
Victor Carroon (as Andy Tiernan)
James Fullalove
Blaker
News Editor
Colonel
Charles Greene
Ludwig Reichenheim
Newsreader
Louisa Greene
Boy
Chemist
Mrs. Matthews
Len Matthews
Journalist (as Susan Sylvester)
Janet
Ted
Park Keeper
Vernon
Inspector
Understudy
Journalist
Soldier (uncredited)