Carter opted for a white T-shirt, gray coat, sneakers and jeans for the occasion, while Cyrus also kept it low-key, sporting a white crop top, a patterned jacket, a brown hat and ripped jeans.
An eyewitness tells ET that Cyrus looked "very happy and playful" with Carter at the party, adding that the women "didn't stay long."
About 20 minutes after Carter and Cyrus made their entrance, onlookers say Jenner, 36, showed up to the same club with his new flame, Josie Canseco, 22. The pair held hands as they entered the venue, with Jenner in an all-black look while his date coordinated with black jeans and a gray crop top.
The two couples stayed for about an hour, before Cyrus and Carter went back to their hotel. Meanwhile, Jenner and Canseco went on to party at another NYC club, Avenue.