When a melting iceberg releases a prehistoric giant praying mantis, a palaeontologist works alongside the military to kill it after it attacks scientific outposts on its way to Washington and New York.
| Actor | Role |
|---|---|
 Craig StevensCol. Joe Parkman | Col. Joe Parkman |
 William HopperDr. Nedrick 'Ned' Jackson | Dr. Nedrick 'Ned' Jackson |
 Alix TaltonMarge Blaine | Marge Blaine |
 Donald RandolphGen. Mark Ford | Gen. Mark Ford |
| FFlorenz AmesProf. Anton Gunther | Prof. Anton Gunther |
 Paul SmithCorporal | Corporal |
 Paul CampbellLt. Fred Pizar | Lt. Fred Pizar |
 Pat ConwaySgt. Pete Allen | Sgt. Pete Allen |
 Phil HarveyLou | Lou |
| HHelen JayMrs. Farley | Mrs. Farley |
 Bing RussellState Trooper | State Trooper |
 David McMahonCapt. Frank Carver | Capt. Frank Carver |
 Marvin MillerNarrator (voice) | Narrator (voice) |
 Michael ForestPhotographer (uncredited) | Photographer (uncredited) |
| SSumner WilliamsC-47 Pilot (uncredited) | C-47 Pilot (uncredited) |