The 50-year-old actress and the 55-year-old actor were at The Beverly Hilton in Beverly Hills, Calif. for Netflix's big soirée.
An eyewitness told E! News Pitt sat at a booth with Leonardo DiCaprio and the rest of their Once Upon a Time...in Hollywood cast. Martin Scorsese and Robert De Niro joined them, as well.
"Brad was in a great mood and very social with everybody—except Jennifer Aniston, who kept her distance at a booth a level up behind Brad," the insider said.
Later on in the evening, Pitt made his way down to the dance floor, where he spoke with a few fans who approached him and posed for some selfies. Aniston sat at a booth with Jason Bateman's wife, Amanda Anka, and Sandra Bullock. Party guests enjoyed a number of appetizers—including egg rolls, fried chicken sliders and zucchini noodles—and sipped on Moet and Chandon champagne.