Bieber, 21, shared on Instagram a black-and-white photo of him and Shanina, reported Ace Showbiz.
In the photo, the "Beauty and a Beat" singer was seen wrapping his hand around Shanina's waist while the 24-year-old model leaned against him.
Justin wore a grey suit with black shirt while Shanina wore a strapless black-and-white gown.
While Justin didn't caption the pic, Shanina reposted the snap along with caption, "Thank you Vegas and @justinbieber for a great weekend wearing @balmainparis #watchinghistory#fightnight#lastnight#mannyvsmayweather #balmain.