Basil Rathbone as Sherlock Holmes

Nigel Bruce as Doctor Watson

Evelyn Ankers as Kitty

Reginald Denny as Sir Evan Barham

Thomas Gomez as R.F. Meade

Henry Daniell as Sir Anthony Lloyd

Montagu Love as General Jerome Lawford

Olaf Hytten as Admiral Sir John Fabian Prentiss

Leyland Hodgson as Captain Roland Shore

Mary Gordon as Mrs. Hudson

Hillary Brooke as Jill Grandis

Harry Cording as Camberwell

Herbert Evans as Smithson - Barham's Butler (uncredited)

Fred Graham as Meade's Henchman (uncredited)

Gavin Muir as BBC Radio Announcer (voice) (uncredited)

Edgar Barrier as Voice of Terror (voice) (uncredited)

Bobby Hale as Bar Patron (uncredited)