The duo defeated Victoria Azarenka and Ash Barty 7-5, 7-5 on Sunday at Arthur Ashe Stadium on Sunday. Mertens and Sabalenka lost only one set in the tournament and won their first Grand Slam title as a team. They faced only one other seeded team on their way to the title.
"From the start of the season, start of the year actually, we were like, we're going to play together,'' Mertens said. "We didn't think we would achieve this big thing.''
Mertens was defeated in singles play in the quarterfinals by Open champion Bianca Andreescu.
"Even if we lose singles, and it's always tough, we still committed to play doubles,'' Mertens said. "Of course in a Grand Slam you want to win, you want to win matches. You want to win this title. So we're just 100 percent committed to both. Of course, singles is a priority still.''