Sean, wearing a pair of Adidas Yeezy 750 Boosts, first assisted his 21-year-old girlfriend on 'Best Mistake', their collaboration from the former Nickelodeon star's latest chart-topping album My Everything, reported Ace Showbiz.
Later, he returned to the stage for 'Right There' off her 2013 debut set 'Yours Truly'.
When performing the latter song, Grande at one point wrapped her arms around Sean's neck and kissed him in front of numerous cheering fans.
"Make some noise for my girl Ariana Grande, y'all!" the 'IDFWU' rapper said to the crowd before leaving the stage.
Sean will also embark on his own tour later this month in support of 'Dark Sky Paradise' that's become his first effort to top Billboard 200.