Jimmy Hunt as David Maclean

Arthur Franz as Dr. Stuart Kelston

Helena Carter as Dr. Pat Blake, MD

Leif Erickson as Mr. George MacLean

Hillary Brooke as Mrs. Mary MacLean

Morris Ankrum as Col. Fielding

Walter Sande as Police Sgt. Mack Finlay

Bert Freed as Police Chief A.C. Barrows

Max Wagner as Army Sgt. Rinaldi

Charles Gibb as Lt. Blair

Milburn Stone as Army Capt. Roth

Douglas Kennedy as Officer Jackson

Charles Cane as Officer Blaine

Fay Baker as Mrs. Wilson

Janine Perreau as Kathy Wilson

John Eldredge as Mr. Turner

Barbara Billingsley as Kelston's Secretary

Richard Deacon as MP

Gil Herman as Major Clary

Luce Potter as The Martian Intelligence

Lock Martin as Mutant Carrying David to 'Intelligence'

Max Palmer as Second Mutant Guarding the "Intelligence"

Todd Karns as Jim the Gas Station Attendant

Frank Wilcox as Pentagon Chief of Staff

Robert Shayne as Dr. William Wilson

William Phipps as Sgt. Baker

William Forrest as Col. Mayberry

Peter Brocco as Brainard (bit)