The famous duel was staged by Hollywood fencing master Fred Cavens. He specialized in staging duels that relied more on real swordplay rather than the jumping on furniture and leaping from balconies that many film duels incorporated up until that point. Cavens' son, Albert Cavens, doubled for Tyrone Power in the fancier parts of the duel (mostly with his back to camera), such as the extended exchange with Esteban ending with Don Diego's sword smashing into the bookcase. Basil Rathbone, a champion fencer in real life, did not care for the saber (the weapon of choice in this film), but nevertheless did all of his own fencing. Fast fencing shots were under-cranked to 18 or 20 frames per second (as opposed to the standard 24fps) and all the sound effects were post-synchronized.
The film is based on "The Curse of Capistrano", written by Johnston McCulley, originally published in 1919 in five serialized installments in "All-Story Weekly", which introduced the masked hero Zorro; the story is set in Southern California during the early 19th century.
Basil Rathbone, being a well-known fencer in his own right, was asked how well Tyrone Power did in their scenes in which stunt doubles were not used. Rathbone responded, "Tyrone Power could fence Errol Flynn into a cocked hat!"
Zorro is Spanish for "fox".