Justin's fans weren't the only ones with a touch of a Bieber Fever when he kicked off his US tour on Saturday.
A video posted on a local TV channel's website shows the pop star being sick twice on stage during the concert.
He had to leave the stage twice, but his fans sang his songs until he came back on.
After the show Bieber tweeted "Great show. Getting better for tomorrow's show !!!!" followed by "And .... Milk was a bad choice!"