Justin co-penned this song during late summer. The teen star explained to MTV News that his secret regarding getting in the Christmas spirit whilst writing for Under the Mistletoe was… Christmas cookies. "It's different, because you've gotta think Christmastime. You've gotta think, 'What's at Christmas? Mistletoe, reindeer, Santa, all these things.' And especially when it's not Christmastime, it's hard to really get your mind around it," he said. "But once you get into it, like, I was really thinking it was Christmastime when I was writing this album. We had Christmas cookies [in the studio]."
Justin wrote this melodic R&B jam with his pal Chris Brown. The pair have collaborated on several previous occasions, including Breezy's track "Next 2 You," which featured Justin and on the remix of "Up" from the Never Say Never - The Remixes album.
Dido helped shut down a Neo-Nazi Web site after learning it was using "White Flag" to promote its hateful messages. Owners of the site had misinterpreted the track as racist and thought they represented their white supremacy views.