The pop star performed at the event after he posed together on the carpet with his wife.
Fashion's biggest night just happened to take place on the same day as the couple's 2018 courthouse wedding ceremony -- and they certainly celebrated in style.
The 27-year-old pop star and 24-year-old model walked the Met Gala red carpet together for the first time as husband and wife, with Hailey in a strapless black Yves Saint Laurent dress and Justin in a wide-legged suit from La Maison Drew, a new branch of his Drew House label.
Hailey posted a photo from the carpet on her Instagram Stories, writing, "Three Years."
"I'm married now, so things have become more adult," Justin told Keke Palmer on Vogue's livestream of his evolving style.
Hailey added that she was going for "timeless American beauty" with her look.
"Both of us love fashion and we love being able to get dressed up and we love collaborating with cool designers and for him to be able to come up with this and debut this new suit," Hailey added, admiring her husband's dapper look.
Once inside the gala, Justin performed for the celebrity crowd, even singing his throwback 2010 hit, "Baby."
Hailey later shared a photo of herself in a white bathrobe with Justin holding her tight, adding a white heart and stars emoji.