Despite its limited release, this movie made more money in its opening weekend than the entire box-office run of Santos Justiceiros (1999).
In Noah MacManus' (Sir Billy Connolly's) voice-over during the drug factory flashback, he says "While the wicked stand confounded, call me, with thy saints surrounded." In Santos Justiceiros (1999), that line is painted above the Irish flag on the wall in the arms dealer's warehouse.
When Connor MacManus (Sean Patrick Flanery) and Murphy MacManus (Norman Reedus) meet Rocco (David Della Rocco) at the bar in their dream, a black cat walks past Rocco across the counter. The cat is a sly reference to Rocco's girlfriend's cat Skippy, who Rocco accidentally shot in Santos Justiceiros (1999).
Versions of the "f" word were only used one hundred thirty-six times in this movie, as opposed to two hundred forty-six times in Santos Justiceiros (1999).
Troy Duffy wrote the part of Romeo, the Saints' sidekick, specifically for his friend Clifton Collins, Jr. Coincidentally, the part of Rocco, the sidekick in Santos Justiceiros (1999), was written specifically, and named for, David Della Rocco.