The talented Italian has been poised to leave Brescia since they were relegated from Serie A in the 2019/20 campaign.
Inter were believed to be leading the pack for the last few months and initially were the first team to agree a fee with Brescia for Tonali.
However, before any deal could be finalised, Milan came in with an improved offer of €35 million. The player himself appeared to have his head turned, too, having grown up as a huge fan of the Rossoneri.
He is set to undergo a medical at the San Siro on Wednesday, and if his social media post is anything to go by, the deal looks signed, sealed, and delivered.
Brescia director Massimo Cellino confirmed that Tonali's desire was to join Milan.
"Sandro has supported Milan since he was a child," he told Il Messaggero.
"The negotiation with them made me doubly happy – I also respect a club that gives value to money."
Despite Brescia's relegation last season, Tonali was a standout performer, with his showings drawing huge praise from around Italy. New Juventus coach Andrea Pirlo, who he has been likened too, insisted Tonali is a more complete player than he was at 20-years-old.