Basil Rathbone as Sherlock Holmes

Nigel Bruce as Dr. John Watson

Hillary Brooke as Lydia Marlowe

Henry Daniell as Professor James Moriarty

Paul Cavanagh as Sir George Fenwick

Matthew Boulton as Inspector Gregson

Eve Amber as Maude Fenwick

Frederick Worlock as Dr. Onslow

Percival Vivian as Dr. Simnell

Coulter Irwin as Corporal Williams

Sally Shepherd as Crandon

Mary Gordon as Mrs. Hudson

John Burton as Waring the Mesmerist (uncredited)

Harold De Becker as Shoelace Vendor Henchman (uncredited)

Tony Ellis as Carter the Hypnotized Subject (uncredited)

Bess Flowers as Bar Patron (seen in mirror) (uncredited)

Kay Harding as 4th Victim (uncredited)

Alec Harford as Commissioner of the CID (uncredited)

Olaf Hytten as Fenwick's Butler Norris (uncredited)

Boyd Irwin as Short-Tempered Officer Closing Window (uncredited)

Eric Mayne as Member of Mesmer Club (uncredited)

William H. O'Brien as Pembrook House Waiter (uncredited)