The newlyweds got into the Halloween spirit by sporting incredibly creepy black-and-white masks to the celebrity hot spot.
You could slightly make out Jennifer, 46, whose bright eyes and blonde hair peaked out from under her skeleton mask. Theroux, on the other hand, was completely in disguise in a fully-covered Dalmatian mask. At least his dapper jacket-and-tie combo wasn't scary!
The couple was at the venue for an after party celebrating the 29th American Cinematheque Awards, which took place earlier that night at the Hyatt Regency Century Plaza Hotel. Guest of honor Reese Witherspoon also made an appearance at the party, along with her Mud co-star, Matthew McConaughey.
An eyewitness tells ET that Jen, who usually hides behind the seat in paparazzi photos, stayed in full view of photographers, showing off her festive ensemble. She and Justin stayed at the party for about an hour and a half before heading home around 1:30 a.m.
Jennifer and Justin -- who tied the knot at their Bel-Air home in August -- haven't been able to stop gushing over married life lately. Earlier this month, Justin made an appearance on The Ellen DeGeneres Show, where he revealed that one of his hobbies gives Jen the spooks -- she's not a fan of his motorcycle.
"She's gotten on like three times, but she's done with it," The Leftovers star said. "She doesn't want to do it anymore."
DeGeneres sided with Justin's wife, reminding the 44-year-old actor that the vehicles can be dangerous. "[Jennifer] doesn't feel in control sitting behind someone driving fast on a motorcycle, which I understand," he added. "I wouldn't want to sit behind someone."