According to multiple reports, the "Ad Astra" star, 55, attended the 50-year-old actress' star-studded holiday party over the weekend, along with about 50 of Aniston's friends.
“The annual tree-trimming party is always Jen’s favorite to host,” a source told People magazine. “She loves Christmas. As usual, a large group of friends attended.”
Along with Pitt, pals Gwyneth Paltrow (whom Pitt also dated in the mid-’90s and the couple was even engaged), Kate Hudson, Jimmy Kimmel and Reese Witherspoon were all also reportedly at the get-together.
An eyewitness told Entertainment Tonight that the actor arrived at Aniston's home in Bel-Air, Calif., "a little after 7 p.m."
"He was among the first to arrive and the second to last guest to leave around 11 p.m," the insider shared. "He was dressed casually in a dark bomber jacket with a cap on. He arrived with his longtime security guard who waited for him with his car and saw him out."
The source noted that it was a "very festive" and "pretty low-key, casual affair." "Just a gathering of close friends to celebrate the holidays," said the insider.
This isn't the first time Pitt has attended one of Aniston's events. According to People magazine, the "Once Upon a Time in Hollywood" star also attended Aniston's 50th birthday celebration in February.
"They have been in touch a few times since her birthday and are keeping it friendly," a source told the outlet of Pitt's most recent appearance.
Aniston and Pitt were married for almost five years, from 2000 to 2005.
Following their divorce, Aniston went on to marry Justin Theroux in 2015. The couple, who started dating in 2011, ultimately split in 2018. Meanwhile, Pitt was with Angelina Jolie for nearly 12 years -- married for two -- before they called it quits in 2016.