Lowe, 55, and Moore, 57, both opted for all-black looks for the occasion, with the actor sporting leather pants, a graphic T-shirt and a stylish jacket. As for Moore, she rocked a sleek dress and fur vest.
At the event -- which was also attended by the likes of Alex Rodriguez, Jennifer Lopez, Kylie Jenner, Miley Cyrus, Kate Hudson and more -- Lowe and Moore were seen laughing and even sharing a kiss on lips in front of the cameras.
Lowe also offered Moore a peck on the cheek. In the background of that particular photo, Moore's daughter, 31-year-old Rumer Willis, and Lowe's son, 25-year-old John Lowe, can be seen excitedly greeting each other.
During the show, the pair sat next to each other in the front row, where they were joined by Willis. The younger Lowe was seated behind the trio.
In her 2019 tell-all memoir, Inside Out, Moore wrote that she "vaguely" recalled having "one ill-advised late night together" with Lowe, before meeting her future fiance, Emilio Estevez, on the set of St. Elmo's Fire.
When ET's Lauren Zima caught up with Lowe last year, he opened up about his time making the movie.
"You could tell we were all really good friends and we all really cared about each other, and that we were a gang," Lowe said. "That's what we played on screen and I think it really was captured."
"It felt like we were all very much in the same place in our lives," Lowe added, referring to his other co-stars, who included Judd Nelson, Andrew McCarthy and Ally Sheedy. "All very ambitious, all looking to the future and wondering what the future would hold."
Watch the video below for more of ET's interview with Lowe.