The exes hit up 1 OAK nightclub in Los Angeles, joined by Kardashian's brother-in-law. An observer tells PEOPLE Kardashian, 36, came in with her friend Brittany Gastineau. Disick, 32, was already there, and Kardashian joined him at his table.
After the rapper, 38, jumped into the DJ booth to drop an unreleased track called "Closest Thing to Einstein" off his still unfinished new album, The Life of Pablo, he headed back to the table where Kardashian and Disick were posted.
The observer says Kardashian and Disick "were extremely friendly" with one another, looking "surprisingly coupled up" and "flirtatious all night."
Courtesy 1 Oak
Courtesy 1 Oak
"Old School Nights With @kourtneykardash and @chad_veach just joined our club #soho nights," she wrote.
It appears that Kardashian and Disick were also together at another point Tuesday evening, hanging with family friend Rich Wilkerson Jr., who officiated Kim Kardashian West and West's wedding.
"My brother," Wilkerson captioned a picture of him and Disick sitting together on a couch.
Kardashian took to Instagram around the same time to post pictures of her, Wilkerson and Veach hanging out on the same couch.
The outing comes just one day after Disick joined the Kardashians to commemorate late patriarch Robert Kardashian on what would have been his 72nd birthday.
Kardashian and Disick – who split in July – gathered with their children Mason, 6, Penelope, 3½, and Reign, 14 months, at momager Kris Jenner's Calabasas home for a special dinner with the rest of the famous family.
Last week, Disick was spotted partying until 5 a.m. in New York City, and a source told PEOPLE "he was a total mess" and Kardashian "won't tolerate" him being around their kids in that state. As for Disick, "he doesn't want to disappoint Kourtney or his kids," the source said.
Disick then returned to Los Angeles, and a second insider told PEOPLE he has "been low-key."