The midfielder is set to make the move to North London as all documents have now been signed between the two Premier League clubs.
It is expected a club statement from Spurs will follow shortly, as per transfer expert Fabrizio Romano.
It comes after Spurs already broke their transfer record in the past week with the signing of Mateus Fernandes from West Ham in an £85 million deal, and now Tonali is set to reinforce Roberto De Zerbi's midfield options heading into the 2026/27 Premier League campaign.
Tonali has been crucial to Newcastle's midfield since signing from AC Milan in 2023 in a £55 million deal, having made 79 Premier League appearances, scoring five goals and providing four assists.
The 26-year-old also helped The Magpies secure their first domestic trophy in 70 years, the 2025 Carabao Cup.
It has been an aggressive start to the transfer window for The Lilywhites, having already brought in Andy Robertson and Marco Senesi, and look set spend a combined £237 million on Paul Van Hecke, Fernandes and Tonali.
Spurs are looking to bounce back from a disaster Premier League season in which they finished 17th, as De Zerbi continues to revamp his squad ahead of the upcoming campaign.