While the Patient Slept

Aline MacMahon Nurse Sarah Keate

Guy Kibbee Detective Lt. Lance O'Leary

Patricia Ellis March Federie, Richard's Granddaughter

Hobart Cavanaugh Eustace Federie

Dorothy Tree Mittie Federie

Robert Barrat Adolphe Federie

Helen Flint Isobel Federie - Adolphe's Wife

Lyle Talbot Ross Lonergan

Henry O'Neill Elihu Dimuck

Walter Walker Richard Federie

Allen Jenkins Police Sgt. Jim Jackson

Eddie Shubert Detective Muldoon

Russell Hicks Dr. Jay

Brandon Hurst Grondal - the Butler

Joseph E. Bernard 'Murph' Murphy - the Ballistics Expert (uncredited)

George Chandler Evening Bulletin Reporter (uncredited)

Nick Copeland Detective Davis aka Johnson (uncredited)

Joseph Crehan Evening Bulletin Editor (uncredited)

Bill Elliott Bank Teller (uncredited)

Virginia Howell Kema - the Cook (uncredited)