The model posted a sweet collage of pictures of her husband as she marked his 26th birthday on Sunday (01.03.20).
Taking to Instagram, she wrote: "Happy birthday best friend. Thank you for putting a smile on my face every single day. I love you."
The 23-year-old model previously confessed she "could not be more proud" of Justin following the launch of his latest album, 'Changes'.
Alongside an image of the album cover, Hailey wrote on the photo-sharing platform: "couldn't be more happy that people can finally hear this album.. could not be more proud of you, could not be more in love with you. congratulations on an amazing amazing album baby. #CHANGES (sic)"
And Justin recently dedicated his new album to his beloved wife.
During an album playback session in London, he shared: "The thought of being with my wife forever gives me chills. This album is obviously dedicated to her and my love towards her."
Meanwhile, the 'Sorry' hitmaker previously admitted he worried he'd be "unfaithful" to his wife and was "extremely nervous" before he popped the question to the model because it was such a "serious commitment".
He explained: "I was extremely nervous. I felt, like, in the past, we talked about, you know, me asking the question and it felt like she would say yes. So, I wasn't really nervous about the saying yes, but the thing is just, like, I think I was more nervous about, 'Am I going to make this commitment? Am I able to make this commitment as a man and be able to honour, you know, what I say?' Because, you know, that's a serious commitment when you say you're going to love someone for better, for worse and, like, be faithful. That's a huge. Am I able to do that? And so, I think that's really what I was battling with.”