In late March 2002, Duffy posted a letter to fans of the first film, claiming that financial backing had been found for a sequel. It would reportedly have twice the budget of the original film, and experience a "theatrical release." According to the film's official website, the release date of the sequel The Boondock Saints: All Saints Day would be September 2005, though this never materialized.
Duffy went on to express his, as well as most of the cast's, interest in making the sequel.
"Everybody's back in except Willem Dafoe, because sometimes actors have their careers plotted out in different ways and he's sort of doing a different thing now. So he's the only one who won't be back. Bill Connolly, the brothers, Rocco, everybody's in and calling me every two weeks and asking when are we going to do this thing."
On June 20, 2008, while being introduced at the Comedy Connection in Boston, Massachusetts, it was stated that Bob Marley was currently in production of the sequel, reprising his role from the first film.
Pre-production on the film started in early September and the first day of shooting was October 20, 2008, and was filmed in Canada. Some scenes may be shot in Boston depending on the film's financing. Duffy has announced that there will be a lead female actress in the sequel (not a love interest). The sequel is supposed to take place 10 years after The Boondock Saints.
On October 29, 2008, Troy Duffy revealed that Julie Benz is going to be the female lead and protégé of Agent Paul Smecker (Willem Dafoe's character from the first film), named Eunice.
"It was going to be released on All Saints Day, because [the film] is called ‘All Saints Day’ ... But now, what I'm hearing is they want to release it earlier, because it's pretty hot."