John Carradine as Prof. Millard Wyman

Robert Clarke as Craig Randall

Phyllis Coates as Dale Marshall

Allen Windsor as Paul Whitmore

Sheila Noonan as Lauri Talbott

George Skaff as Dr. J.R. Matheny

Maurice Bernard as Old Man in the Caverns

Joe Maierhouser as Jim Wyman

Lloyd Nelson as Wilson, Sonar Man

Harry Raven as The Captain

Milt Collion as Hank

Lowell Hopkins as Reporter

Jack Haffner as Jimmy, Reporter

Robert Carroll as Narrator