"We are delighted to announce that we have reached agreement for [Yang] to join the club," the English premier club also said on their X account.
Details of the six-year deal which runs until 2030 have not been revealed yet, but the transfer fee is reportedly the largest among Spurs players under 18. Yang is expected to head to London early next year.
Still a high-school student, Yang made his debut at the start of this year's K-League season, and just turned professional last month.
With the latest deal, the forward becomes the third Korean to don a Spurs jersey, following defender Lee Young-pyo in the early 2000s and the team's current caption Son Heung-min.
Meanwhile, Tottenham players, led by coach Ange Postecoglou, arrived in Seoul the same day as part of their pre-season tour of Asia.
