Guy Pearce admitted that he had trouble getting the accent of the Reverend right, who is supposed to be Dutch. He called it one of the hardest accents in the world, but worked hard to get as close as he could, hoping that Dutch audiences would forgive him if it did not sound completely right.
Carice van Houten and Guy Pearce became romantically involved on the set. They missed the movie's premiere at the Venice Film Festival because their son, Monte Pearce, had been born just five days before (director Martin Koolhoven nicknamed him 'the Brimbaby').
The movie's chapters would originally follow each other much faster. It was composer Tom Holkenborg who suggested to put a few seconds of black screen in between, in order to give the audience some time to breathe.
Director Martin Koolhoven had been preparing the movie for 5 years, and had invested some of his own money in it. A cancellation would mean that he would be financially ruined himself, and he would lose the rights to his own screenplay. When funding for the movie almost fell through at the eleventh hour, he had to go to the hospital with symptoms of a heart attack. Fortunately, it turned out to be a panic attack from all the stress. Koolhoven maintains that although it may have seemed in the media that making Brimstone was a living hell (also due to some last-minute cast replacements), once the biggest hurdles had been taken, he had the time of his life filming his dream project with a wonderful cast and crew. Moreover, he was extremely happy to be able to shoot scenes in Almeria, Spain, where his favorite movie Once Upon a Time in the West (1968) had been filmed as well.
Mia Wasikowska and Robert Pattinson were supposed to star as Liz and Samuel respectively, but got replaced by Dakota Fanning and Kit Harington just before shooting was supposed to begin. Wasikowska backed out of the production due to "unforeseen personal circumstances". When one of the movie's financiers subsequently pulled out, the movie was nearly bankrupted before any footage was shot, since crew and equipment had already been hired and complete sets had been built. When Guy Pearce took the plane to come to Europe, he took a huge risk, because the financing was not completely in place. However, he had been very enthusiastic about his Reverend character since meeting with director Martin Koolhoven, and his presence was a deciding factor in securing the rest of the budget. Within a few days, Wasikowska was replaced by Fanning (who had already been considered for the part, but had availability problems before), but then Pattinson suddenly backed out. Luckily, Harington was prepared to cut his holiday short, leaving him only a few days to get to the set and prepare for filming. In a 2017 interview, Robert Pattinson stated he had backed out because he thought the movie would be canceled after Wasikowska pulled out, and that by the time the production got back on track again, his schedule was too tight because of his involvement in The Lost City of Z (2016). He said that it was "his own, stupid fault" and that he regretted not doing the movie.