The pop star, who recently turned 17, walked the red carpet with girlfriend Selena, 18, at the Oscars where they finally confirmed that they are dating by putting on several public displays of affection.
A source said to UK newspaper Daily Mirror: 'Justin has been wanting to go public with Selena for months, but it wasn't until now that they finally felt the time was right.
'Selena was delighted when Justin asked her to go as his date a few weeks ago. They spent the whole night wrapped up in each other, with Bieber introducing her to his famous pals as his 'hot girlfriend'.
'They giggled in the corner, writing secret messages to each other on their mobiles. Selena didn't let go of his hand all night. Then Justin pulled her into a photobooth where they took some snaps. They're clearly smitten.'