Sal Mineo
as John "Plato" Crawford
Jim Backus
as Frank Stark
Ann Doran
as Mrs. Stark
Corey Allen
as Buzz Gunderson
William Hopper
as Judy's Father
Rochelle Hudson
as Judy's Mother
Jack Simmons
as Cookie
Jack Grinnage
as Moose
Beverly Long
as Helen
Steffi Sidney
as Mil
Frank Mazzola
as Crunch
Tom Bernard
as Harry
Clifford Morris
as Cliff
Robert Foulk
as Gene
Jimmy Baird
as Beau (uncredited)
Nelson Leigh
as Desk sergeant No. 1 (uncredited)