Voice of the Whistler: Reparto
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)
Otto Forrest
The Whistler (uncredited)
Byron Foulger
Georgie (uncredited)
Martín Garralaga
Tony, Fruit Peddler (uncredited)
John Hamilton
Doctor (uncredited)
Stuart Holmes
Sinclair Executive (uncredited)
Wilbur Mack
Sinclair Executive (uncredited)
Charles Marsh
Sinclair Executive (uncredited)
Harold Miller
Sinclair Executive (uncredited)
Forbes Murray
Sinclair Executive (uncredited)
Gigi Perreau
Bobbie (uncredited)
Frank Reicher
Dr. Rose (uncredited)
Clinton Rosemond
Train Porter (uncredited)
Frank J. Scannell
Druggist (uncredited)
Minerva Urecal
Georgie's Wife (uncredited)
Robert B. Williams
Pharmacist (uncredited)
Douglas Wood
Paul Kitridge - Attorney (uncredited)