The reality star was spotted getting up close and cozy with a "mystery girl" -- later identified as Emma Blanchard -- during an exclusive party at #clubREVOLVE, hosted by REVOLVE and 1Oak, in the Hamptons on Saturday.
An eyewitness tells ET that the pair arrived to the party together in the same SUV around midnight, and were spotted openly making out in the club while drinking Ciroc cocktails and Moet & Chandon rose champagne.
"At one point, Scott and Emma slipped into a room behind a curtain to get more privacy," the eyewitness shared. "[They left] together, hand in hand, at 3 a.m."
The pair were photographed, separately, hanging out at the party with friends. Blanchard, a journalist and writer for V Magazine, rocked a black romper with a plunging neckline, cinched at the waist with a black belt, as she posed on a couch with model Maia Cotton.
"It’s never an easy thing to watch someone you share three children with, and so many memories, move on with someone else," a source recently told ET. "Scott has had a hard time watching Kourtney move on while he is in the same place he’s been in for years. It’s been tough for him."
Check out the video below to hear more about Disick's attempts to move on with his love life.