Helping out his own mentor, Justin Bieber will be returning to The X-Factor for the second season in a row, only this time not as a performer, but as a celebrity guest mentor. America's No. 1 pop star is set to mentor L.A. Reid's contestant group and will appear on the show during the judges' house round.

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Justin tweeted about his latest project, writing, "long day but great day.   just like old times! thanks"

During the judges' house round four contestants -- picked by the judges -- get to compete for a spot in the final 16. While Justin is helping out with Reid's group, another BIG name singer, Nick Jonas, will be stepping up as a celeb mentor also, rumored as Demi Lovato's group mentor, Gossip Cop reports.

Talk about a dream come true.... Could you image working with Justin Bieber or Nick Jonas?

Photo courtesy of Fame/Flynet