Disick, 33, was spotted out in Los Angeles with his rumored girlfriend, 19-year-old British model Ella Ross, on Friday just days after Kardashian stepped out in public with model and former boxer Younes Bendjima, Us Weekly reported.
Disick and Ross were photographed going to lunch together at Nobu restaurant on Cinco de Mayo followed by dinner at TAO Asian Bistro.
Disick was sporting a casual outfit in which he was wearing light blue jeans, white sneakers, and a white, pink and red Fila hoodie over a white T-shirt.
Meanwhile, Ross rocked black Adidas track pants with what appeared to be a netted bodysuit underneath. The model completed her look with a black-lace crop top, matching sandals, and a large handbag.
Just three days before Disick and Ross' outing, his ex was photographed with 23-year-old Bendjima in West Hollywood. Bendjima also reportedly celebrated Kardashian's 38th birthday last month at Chateau Marmont.
"Kourtney and Younes are not serious," a source told Us. "They are hooking up."
Disick felt "betrayed" and "devastated" by theKeeping Up with the Kardashians star's fling with Bendjima, according to TMZ, because the self-proclaimed Lord held out hope Kardashian would give him another chance and they'd get back together if he could prove himself worthy.
Kardashian and the former boxer have been involved since October 2016, TMZ reported, which is well over a year after the reality TV star split from Disick -- the father of her three kids Mason, 7, Penelope, 4, and Reign, 2 -- in July 2015.
Kardashian reportedly pulled the plug on their romance of nearly a decade when he was spotted getting touchy-feely with his ex-girlfriend Chloe Bartoli in Monte Carlo.
Kardashian also struggled to deal with Disick in light of his former substance abuse issues.
"For him, it's fine to hang out with girls, but when Kourtney does, he pouts," a People insider said of Disick, adding that he's being a "typical guy" about the situation.
"Kourtney doesn't care what he thinks," noted the insider. "She just thinks he is the last person who should have any opinions about who she is dating."