Pitt was photographed at the party, keeping a low profile with his long hair slicked back and hidden under a baseball cap.
The event marked a milestone birthday for Jennifer, prompting her to celebrate with all of the people who have had an impact on her life, People magazine reports.
In addition to Pitt, 55, a slew of Aniston's famous friends, including Kate Hudson, Jason Bateman and Reese Witherspoon, who appeared to take a tumble on the stairs, toasted the birthday girl, who turns the big 5-0 on Monday. "She had some family there and seemed very happy to be with so many good friends", the insider noted.
"Love these ladies", Hudson wrote.
Her star-studded birthday party was given a strict social media ban.
She certainly wasn't alone when she left last night's party - the star was surrounded by pals. "We love you so much and you make 50 LOOK [fire emoji]".
Brad and Jen were once Hollywood's darling couple but ended their marriage in 2005 after five years.
"My marriages, they've been very successful, in personal opinion".
Opening up about her two divorces-the actress was also married to Justin Theroux from 2015 until 2018-Aniston told ELLE, "I don't feel a void. And when they came to an end, it was a choice that was made because we chose to be happy, and sometimes happiness doesn't exist within that arrangement anymore", she explained.
Pitt and Aniston were together way back in the heyday of Friends, when Pitt even co-starred on the show.