The 21-year-old is Tottenham’s sixth summer signing, following Fraser Forster, Yves Bissouma, Ivan Perisic, Richarlison, and Clement Lenglet.
Spence spent the 2021-22 season on loan at Nottingham Forest, where he was instrumental in the Tricky Trees’ promotion to the Premier League.
Spence had three goals and five assists in 46 games for Steve Cooper’s side, which also reached the FA Cup quarter-finals before losing to Liverpool.
The England Under-21 international was a Fulham academy product before joining Middlesbrough in 2018, where he scored two goals in 70 Championship appearances.
Spence’s exploits earned him a spot in the EFL Championship Team of the Season as well as the PFA Championship Team of the Year for the 2021-22 season.
Spurs have confirmed that Spence has signed a five-year contract extension until the summer of 2027, despite the fact that the North London club initially struggled to reach an agreement with Boro.
Spurs chairman Daniel Levy was leading negotiations with Chris Wilder’s side while Fabio Paratici focused on other targets.
However, Tottenham and Middlesbrough reached an agreement last week, and the North London club will reportedly pay an upfront fee of £12.5 million for the defender.
Boro could earn up to £20 million in performance-related bonuses, and the strong relationship between Levy and his Middlesbrough counterpart Steve Gibson was said to be crucial in completing the deal.
North London rivals Arsenal were also said to be interested in signing Spence, but Tottenham quickly outpaced their capital rivals in the race.
Spence will arrive in North London to compete for the right-wing back position with Lucas Moura, Matt Doherty, and Emerson Royal, the latter of whom is still linked with a move away.
Spence’s media duties were leaked on social media before his signing was announced, and the youngster could now make his debut against Rangers at Ibrox on Saturday.