The pop star, who is staying on South Beach at the SLS Hotel, visited Mansion for the nightclub's Hot Excess Mondays hip-hop party.
“Justin arrived at 3:45 a.m. with three SUVs of friends, including Young Money artist Lil Twist,” a source tells PEOPLE.
The group sat in the V.I.P. area, where Bieber sipped water and watched live performances by Rocko, Pleasure P and Flo Rida, who was shouting out at the crowd and celebrating Miami’s win.
“Bieber was surrounded by an ever-growing group of girls, talking to one unknown girl in particular, but also spent time texting and enjoying the music on stage,” the source adds. “He stayed until the lights came on at 5 a.m., closing Mansion down."
Game 7 Tonight. Who you guys got?— Justin Bieber (@justinbieber) June 3, 2013