Voice of the Whistler

Richard Dix

John Sinclair / John Carter

Lynn Merrick

Joan Martin Sinclair

Rhys Williams

Ernie Sparrow

James Cardwell

Fred (Doc) Graham

Tom Kennedy

Ferdinand / Hammerlock

Sam Ash

Gibson Motor Car Co. Executive (uncredited)

Egon Brecher

Dr. Rose (replaced by Frank Reicher) (uncredited)

Charles Coleman

Sinclair's Butler (uncredited)