The pair got engaged back in July, and speculation began swirling that they may have tied the knot after they were seen visiting a marriage license courthouse in Manhattan. Hailey hit back at the rumours at the time, but now TMZ.com have reported that the claims are actually true.
According to the website, preacher Jeffrey Quinn, a member of the Nyack College near the courthouse, was on hand for the ceremony, while Josh Mehl, Justin's friend from Churchome in Los Angeles, acted as witness.
TMZ adds that while both Justin and Hailey reached out to their lawyers in a bid to get a prenuptial agreement in place on the day they exchanged vows, they left it too late to get the paperwork in place.
And somewhat unusually, the newlyweds have apparently opted against arranging such an agreement, called a postnuptial, now they are officially husband and wife. An insider told TMZ that "Justin is so in love he doesn't see the need for one".
Justin and Hailey are now said to be planning to have a formal wedding ceremony, but it will "be a ceremony in name only because they are already husband and wife".
The news comes after the "Sorry" singer referred to model Hailey as his "wife" while visiting the Stratford Perth Museum in his home state of Ontario on Sunday.
Officials at the museum said on social media that Justin "'very graciously introduced Hailey as his wife," according to The Windsor Star newspaper.
Justin also left a message for Hailey on a chalkboard at the exhibit dedicated to his career, which the museum shared on their official Instagram page on Monday. "I (heart) you forever-Hailey B'. We were so pleased to have such a warm and special guest visit the museum yesterday (along with her very special husband) @haileybaldwin @justinbieber," they captioned the picture.
According to museum manager John Kastner, Justin and Hailey spent around 45 minutes looking around the exhibit and meeting fans. They were later seen heading to a local airport where they boarded a private jet.