The teenage pop star is currently working on the follow-up to his hit album My World 2.0. and he's collaborating with Garrett, who has written songs for Usher, Ciara and Britney Spears.
Garrett admits 16-year-old Bieber is aiming for a more grown-up sound on the new record, and they are looking to Timberlake for inspiration.
"The one great thing about Justin Bieber is the fact that his fans are going to grow with him"
He tells Billboard, "What we're trying to do with Justin is to segue him into young adulthood. The one great thing about Justin Bieber is the fact that his fans are going to grow with him. So we want all the fans thatstarted out with him to still be intrigued and excited about him, but wewant to also stretch out a little bit and make the fans that are 22-23 years old love Justin as well.