Brian Donlevy

Prof. Bernard Quatermass

Richard Wordsworth

Victor Carroon

David King-Wood

Dr. Gordon Briscoe

Jack Warner

Inspector Lomax

Margia Dean

Judith Carroon

Maurice Kaufmann

Marsh

John Wynn

Detective Sergeant Best

Harold Lang

Christie

Lionel Jeffries

Blake

Thora Hird

Rosie Wrigley

Sam Kydd

Police Sergeant Questioning Rosie

Jane Asher

Little Girl (uncredited)

Toke Townley

The Chemist (uncredited)

Gordon Jackson

BBC TV producer

Margaret Anderson

Maggie (uncredited)