
Italy international Tonali joined Newcastle from AC Milan for £55m in July 2023.
He was banned for 10 months by the Italian Football Federation (FIGC) for breaching betting rules shortly after his arrival.
But he became a key player on his return and helped Newcastle win the Carabao Cup in 2025 - their first trophy in 70 years.
In a social media post,, external Tonali said it was "time to say goodbye" to the Magpies and manager Eddie Howe, although "it's hard to find the right words" as he also thanked the club's fans for their support.
"Thank you to the staff and my team-mates for believing in me and helping me grow," he wrote.
"A special mention to the gaffer, Eddie, who's been a real guiding figure and who always had my back throughout this journey.
"This city gave me more than football. It gave me a home, moments I'll hold onto forever, and people I will always be grateful for. Thank you for everything."
Spurs boss De Zerbi, who took over at Tottenham at the end of March and narrowly saved the club from Premier League relegation, described Tonali as a "special player".
He added: "I have followed him for a long time, as he came through the youth system at my hometown club, Brescia, and I'm so happy to be working with him now.
"Given his qualities, there was a lot of interest in Sandro this summer. However, he was very clear in his desire to join Tottenham, and I know our fans will love what he brings to the team."
It has been a busy summer for Tottenham after they finished 17th - and two points above the relegation zone - in the Premier League last season.
Defenders Andy Robertson and Marcos Senesi have arrived on free transfers and the club could end up spending a combined £237m on centre-back Jan Paul van Hecke and midfielders Fernandes and Tonali.
"He [Tonali] has outstanding technical quality to go with real football intelligence, and has the character to thrive in a demanding, high-pressure environment," said Spurs sporting director Johan Lange.
Football finance expert Kieran Maguire
Tottenham can spend significant sums because under the new squad-cost ratio rules (SCR) they are allowed to spend up to 85% of their revenue on player costs - player wages, amortisation and agent fees etc.
In their last set of accounts (2024-25), wages and amortisation was only 61%, and this includes all salaries. Clubs do not separate between playing and non-playing staff, although Uefa says that normally about 75% of total wage costs go towards a club's first team.
In addition, Tottenham's new stadium, which can now host up to 30 non-football events a year at full capacity, is proving to be very beneficial.
At their old White Hart Lane ground, annual matchday revenue was £45m and commercial income - which includes concerts and NFL games - was £73m.
At the new stadium those figures were £126m and £277m, respectively, in 2024-25. The additional money coming into the club allows it to spend more under the SCR regime.
While the club has spent a lot of money this summer to date, transfer fees are amortised over the length of the contract, but limited to five years, so a £240m spend this summer equates to a £48m amortisation fee.
Tottenham's total revenue for 2024-25 was £565m. Under SCR rules they would be able to spend up to £480m a year on their squad.
View original source — BBC Sport ↗