Bieber Fever came to the UK this weekend as Justin Bieber hit the stage at Radio 1's Big Weekend festival.
Radio 1 DJs showed that they also had a case of the Bieber Fever, flashing their T-Shirts before his performance.
The crowd screamed with excitement as the teen sensation and his dancers performed on stage.
Justin sung three songs from his My World album, ending with his massive hit single 'Baby'.
Somebody to Love? Justin asks if his number one girl is in the crowd.
The Canadian pop sensation has a team of people who travel with him to make sure he stays safe.
After his amazing set Justin came back stage to have his picture taken by lots of photographers.
Newsround had a chat with him to find out what he thinks of Bieber Fever and what it's like to be on the road all the time.
Justin told us he can't live without his computer when he is on tour and that he passes the time by tweeting!
He also told us about his funky yellow trainers... but to find out more you'll have to watch out for our interview!