The archery tournament was shot at the now gone Busch Gardens in Pasadena, CA, which was later used for the Wilkes plantation exteriors in Via col vento (1939), among many other films.
During one fight sequence, Errol Flynn was jabbed by an actor who was using an unprotected sword--he asked him why he didn't have a guard on the point. The other player apologized and explained that director Michael Curtiz had instructed him to remove the safety feature in order to make the action "more exciting". Flynn reportedly climbed up a gantry where Curtiz was standing next to the camera, took him by the throat and asked him if he found that "exciting enough".
According to TCM host Robert Osborne, the film was so successful that a sequel was commissioned. However, the US government wanted to restrict the amount of money invested in filmmaking at that point in anticipation of joining World War II, so it was delayed. By 1945, when the war was over, the project was scrapped because Olivia de Havilland and Claude Rains were no longer employed at Warner Bros.
The production used all 11 of the Technicolor cameras in existence in 1938 and they were all returned to Technicolor at the end of each day's filming.