Taylor Swift surprised fans on the second of her four sold-out shows in Los Angeles when the 21-year-old brought out Jason Mraz to perform a duet of his hit single 'I'm Yours.'

The duo wowed audiences at the Staples Center with their rendition of the 2008 song, which Mraz performed standing and playing acoustic guitar. Swift sat on a stool beside her singer-songwriter pal, singing a verse and harmonizing on the chorus of the tune.

The country star, who has been known to cover hometown artist during her Speak Now tour, floored fans when she brought Justin Bieber on stage on Tuesday to perform his 'My World 2.0' smash, 'Baby.' The duo sang the song together, but Swift let the 17-year-old take the lead on the pop track.

Swift is scheduled for two more nights at the LA arena this week. Judging by her established trend, she will likely bring two other big name acts on stage for her shows on Saturday and Sunday.

At this point, her guests could be anyone, but going by her young fanbase and recent picks, we think she'll continue her pop artist trend for her remaining SoCal dates. The Speak Now tour will continue through the US this fall, wrapping on Nov. 21 and 22 in New York City.

Watch Taylor Swift Perform 'I'm Yours' With Jason Mraz