We're told that Theroux flew into the Big Easy on Thursday morning and spent a few days hanging out with the groom and other guy friends, "having dinner and socializing during the day."
Aniston remained in L.A., where the betrothed couple are in the process of moving into their newly renovated home in Bel-Air, before hopping a private jet to New Orleans on Saturday afternoon, our source says.
The We're the Millers star was greeted by security at the airport and she went straight from there to the Marigny Opera House, arriving just in time for the 7 p.m. ceremony.
Theroux was in the wedding party and, per the eyewitness, was busy pulling usher duty, which at one point included attending to two dogs that also played a role in the Bell-Campbell nuptials.
Once there, Aniston hung out with fellow guest Cameron Diaz, who was trailed by security at all times and kept her sunglasses on "a lot," the witness says.
Theroux and Aniston did not, however, stick around for Sunday brunch, our source telling us that they instead flew back to L.A. at around noon.