Mobile phone video popped up across the Web on Monday showing a male fan rushing toward the 19-year-old performer, who was sitting at a piano on the edge of the stage.
Security guards tackled the young man from behind, spilling into Bieber and tipping over the piano.
Bieber twisted away and then strolled offstage while the guards dragged away the fan.
The concert Sunday - the second of a two-performance stand in Dubai - resumed after a short break and Bieber appeared calm and unharmed.
He later tweeted: "Dubai. Nothing stops the show."
