The 16-year-old star will perform in the next results show and he recently said he loves the Brazilian singer that has outraged the judges.
He said to UK newspaper The Sun: 'I know he isn't the best singer, but the public want him there. The judges should chill out a bit.'
Judge Cheryl Cole, 27, recently hit out at Wagner live on air after he reportedly made comments that she was just a girl from a council estate who 'got lucky'.
But Bieber said: 'I thought she was a little mean to him. He just seems humble and happy to be there.'