Basil Rathbone was forced, due to scheduling conflicts, to simultaneously work on Rio during the first week of production. Rathbone's assignment on this film also effectively prevented him from being cast on the far more prestigious The Hunchback of Notre Dame at RKO.
Vincent Price later admitted the "wine" he got drunk with in the film was Coca Cola.
After a preview screening in November, 1939, studio heads were alarmed that the score contained nothing but period music and ordered a new score be written. Time considerations ultimately prevented this, with Frank Skinner cobbling together pieces from his score from Son of Frankenstein. Only pieces of the original score survived the final cut.
Production wrapped on 4 September 1939, 10 days and nearly $80,000 over budget.
The August 3, 1939 Louella Parsons column announced that George Sanders was to play Edward IV. The part ultimately went to Ian Keith.
The battle scenes were an ordeal to film. Principally shot on August 19, 1939 at a ranch in Tarzana, the fog machine proved ineffective in the face of high winds. The 100-degree heat caused the 300 extras to suffer and rain machines caused the soldier's cardboard helmets and shields to disintegrate. Additional battle scenes were shot on August 22 and on September 4, 1939, but the California heat continued to play havoc with the cast, crew and equipment.