The teenage popstars have been together since March this year, and Bieber confessed his affection for the 'Naturally' singer during a recent interview.
"I wouldn't be with somebody if I wasn't in love," Bieber told New magazine.
"Everybody can see she is hot and that's great, but there is so much more to her than that. She makes me laugh and she puts up with my practical jokes.
"We were both raised by our mums in single-parent households, and that's given us a lot of the same family values in life."
Bieber went on to explain that although the couple's hectic work schedules make it difficult to spend time together, they try to make time to do normal things.
The 17-year-old recently suggested that he hopes to be married by the age of 25 .
Watch Justin Bieber perform his new Christmas single 'Mistletoe' live below: