Justin Bieber made a surprise appearance at Taylor Swift's concert last night.

The 'Never Say Never' singer stunned the 'Love Story' hitmaker and her fans by arriving on stage to sing his song 'Baby' with her at the concert which took place at Los Angeles' Staples Center.

After the show, the 21-year-old country musician wrote on her twitter page: "You think you've heard LOUD screaming in your life. Then @justinbieber comes out and does a surprise song during your show. Woah. Unreal. (sic)"

In response to Taylor's tweet, the 17-year-old teen heartthrob replied: "@taylorswift13 we should do that more often. :) great show! #muchlove. (sic)"

Taylor is close friends with Justin's girlfriend Selena Gomez and the singer-and-actress recently revealed the 'Mine' hitmaker is always there for her whenever she needs some advice.

Selena explained: "Every problem I ever have is healable by Taylor Swift. When Taylor was going through a hard time breaking up with Joe Jonas, we'd make each other playlists. I'd send her some girl-empowering music and she'd send some back.

"What I love about Taylor is that she believes in the whole love story - Prince Charming, soul mates. Because of her, I haven't lost faith."