Ronald Colman as Dr. Martin Arrowsmith

Helen Hayes as Leora Tozer Arrowsmith

Richard Bennett as Gustav Sondelius

A.E. Anson as Professor Max Gottlieb

Clarence Brooks as Dr. Oliver Marchand

Alec B. Francis as Twyford

Claude King as Dr. Tubbs

Bert Roach as Bert Tozer

Myrna Loy as Joyce Lanyon

Russell Hopton as Terry Wickett

David Landau as State Veterinarian

Lumsden Hare as Sir Robert Fairland

Erville Alderson as Pioneer (uncredited)

Ward Bond as Cop (uncredited)

Beulah Bondi as Mrs. Tozer (uncredited)

Florence Britton as Miss Twyford (uncredited)

Nora Cecil as Nurse (uncredited)

Sidney De Gray as Dr. Hesselink (uncredited)

Cyril Delevanti as Committee Member (uncredited)

Walter Downing as City Clerk (uncredited)

Gibson Gowland as Committee Member (uncredited)

Sherry Hall as Reporter (uncredited)

Theresa Harris as Native Mother (uncredited)

Raymond Hatton as Drunk (uncredited)

Charlotte Henry as Pioneer Girl (uncredited)

George Humbert as Italian Uncle (uncredited)

DeWitt Jennings as B.W. Tozer (uncredited)

Mike Lally as Reporter (uncredited)

Lillian Lawrence as West Indies Townswoman at Meeting (uncredited)

Carl M. Leviness as Ship's Passenger (uncredited)

James A. Marcus as Old Doctor (uncredited)

Eric Mayne as Dignitary at Luncheon (uncredited)

Kendall McComas as Little Johnny (uncredited)

Edmund Mortimer as Ship's Passenger (uncredited)

John Qualen as Henry Novak (uncredited)

Edward Reinach as Dignitary (uncredited)

Milton Royce as Intern (uncredited)

Harry Schultz as Bartender (uncredited)

Pat Somerset as Ship's Officer (uncredited)

Adele Watson as Mrs. Novak (uncredited)

Bobby Watson as Little Neighbor (uncredited)

Eric Wilton as Ship's Officer (uncredited)