Jack Arnold Director Arthur Franz Prof. Donald Blake Actor Joanna Moore Madeline Howard Actor Judson Pratt Lt. Mike Stevens Actor Nancy Walters Sylvia Lockwood Actor Troy Donahue Jimmy Flanders Actor Phil Harvey Sgt. Powell Actor Helen Westcott Nurse Molly Riordan Actor Alexander Lockwood Prof. Gilbert Howard Actor Whit Bissell Dr. Oliver Cole Actor Ross Elliott Sgt. Eddie Daniels Actor Eddie Parker Donald as a Monster Actor Hank Patterson Townsend Actor David Duncan Screenwriter Joseph Gershenson Producer Russell Metty Cinematographer Ted J. Kent Film Editing Alexander Golitzen Art Director Russell A. Gausman Set Decoration Julia Heron Set Decoration