Ronald Colman

Dr. Martin Arrowsmith

Helen Hayes

Leora Tozer Arrowsmith

Richard Bennett

Gustav Sondelius

A.E. Anson

Professor Max Gottlieb

Clarence Brooks

Dr. Oliver Marchand

Alec B. Francis

Twyford

Claude King

Dr. Tubbs

Bert Roach

Bert Tozer

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)

Florence Britton

Miss Twyford (uncredited)

Nora Cecil

Nurse (uncredited)

Sidney De Gray

Dr. Hesselink (uncredited)

Cyril Delevanti

Committee Member (uncredited)

Gibson Gowland

Committee Member (uncredited)