The surprise concert in Venice Beach attracted quite an entourage.
MGK's girlfriend Megan Fox and Barker's girlfriend Kourtney Kardashian were both in attendance, as well as Kardashian's good friend Addison Rae. The women were all smiles on the rooftop while listening to the guys play at the show, which was put on by NoCap.
Fox, 35, wore a long trench coat over a tan crop top and jeans for the outing, while Kardashian, 42, sported a black-and-red striped sweater. Rae, meanwhile, put her abs on display in a black top and black pants.
This isn't the first time Kardashian and Fox have hung out. The two enjoyed a night out with their boyfriends at UFC 260 in March.
Barker and Kelly have known each other for years, having collaborated on several projects. They most recently worked together on MGK's album, Tickets to My Downfall.
"Kourtney Kardashian, Travis Barker, Megan Fox and MGK have had double date nights many times and are all good friends," a source told ET in March. "They have a great time when they hang out as couples and it's very natural, easy and fun. They all have a lot of shared interests like music, self-care practices and more. Kourtney and Travis are super into each other and Megan and Machine Gun Kelly are so in love. So it's nice for both couples to spend time with like-minded people."
See more in the video below.