The film was released on September 1, 1939, the same day as the German invasion of Poland.
Based on an 1899 stage play by William Gillette which--famously--was the stage debut of Charles Chaplin, playing the character of Billy. Terry Kilburn plays the character in the film.
Lionel Atwill was originally cast as Prof. Moriarty, but was replaced before shooting by George Zucco. However, Atwill would go on to play Moriarty in Sherlock Holmes and the Secret Weapon (1942) also starring Basil Rathbone and Nigel Bruce as Sherlock Holmes and Dr. Watson, respectively.
This was the first adaptation where Sherlock Holmes uttered the phrase, "Elementary, my dear Watson", which was never uttered in the original stories.
Through what can only be seen in retrospect as mishandling by Fox, the film was relegated to second bill status upon release and considered a failure by the studio, which cancelled its planned series of Holmes adaptations.