Ronald Colman

Dr. Martin Arrowsmith

Helen Hayes

Leora Tozer Arrowsmith

Claude King

Dr. Tubbs

Myrna Loy

Joyce Lanyon

Russell Hopton

Terry Wickett

David Landau

State Veterinarian

Lumsden Hare

Sir Robert Fairland

Erville Alderson

Pioneer (uncredited)

Ward Bond

Cop (uncredited)

Beulah Bondi

Mrs. Tozer (uncredited)

Nora Cecil

Nurse (uncredited)

Cyril Delevanti

Committee Member (uncredited)

Gibson Gowland

Committee Member (uncredited)

Raymond Hatton

Drunk (uncredited)

DeWitt Jennings

B.W. Tozer (uncredited)

Mike Lally

Reporter (uncredited)

Carl M. Leviness

Ship's Passenger (uncredited)

Eric Mayne

Dignitary at Luncheon (uncredited)

Kendall McComas

Little Johnny (uncredited)

John Qualen

Henry Novak (uncredited)

Eric Wilton

Ship's Officer (uncredited)