The 16-year-old sang a medley of his hits Baby and Somebody to Love but after his performance he flirted with The Flood singer.
While waving at Cheryl and raising his eyebrows, Bieber said: 'I want to say hello to Cheryl Cole, hello.'
Cole, 27, laughed it off while Justin signalled for her to call him.
He later tweeted: 'Cheryl you looked lovely as usual.'
The Canadian singer also wrote on his Twitter page about X Factor boss Simon Cowell being a fan of his.
He added: 'X Factor we had fun. Simon told me he listens to my CD every night before he goes to bed.'