Selena reportedly flew in from Florida, where she’s currently filming Spring Breakers, especially for the occasion.
The 19-year-old wore a red strapless gown while her beau opted for a black and white dogtooth jacket and an Elvis hairstyle.
Justin, who celebrated his birthday on March 1, could be seen planting numerous kisses on his girlfriend’s cheek.
Photos of the couple’s PDA surfaced on Twitter.
“NO MATTER WHAT WE PARTY TONIGHT,” the Biebs tweeted before the party and later signed off from the social networking site, writing “#greatnight.”
As for Selena, she didn’t miss on the chance to profess her love via Twitter, writing “Happy birthday to my best friend in the world world!!! Have a great birthday baby!”