on 1 february 2016, de laet joined championship side middlesbrough on loan for the remainder of the 2015–16 season. he won promotion with the team on the final day of the season, after a 1–1 draw with brighton & hove albion. this meant that de laet achieved the unique feat of winning promotion from the championship and then winning the premier league title, courtesy of his 12 league appearances for leicester in the same season.