Diawara, born in Paris on January 13, 2006, came through the academies of FC Solitaires Paris and CA Paris-Charenton before joining Troyes' youth setup in 2020, making his first-team debut in November 2024 in the Coupe de France.
The move is a permanent transfer worth around €3 million, with Diawara handed the number 13 shirt on a contract running until June 2031. He went on to help the club win the Ligue 2 title and secure promotion to Ligue 1 last season, making 17 appearances across the league and domestic cup.
He is AC Milan's third signing of the summer, following Mario Gila and Gonçalo Ramos, and had also been attracting interest from Rangers before opting for San Siro.
A left-footed defender capable of playing at centre-back or left-back, Diawara gave his first comments as a Milan player through the club's official channels.
"I believe the day I see San Siro will stay etched in my mind forever. I can't wait to make my debut and meet the Rossoneri fans, my team-mates and the whole staff. I've loved football since I was a boy and, little by little, I'm living out my childhood dream.
"I was born with a ball at my feet, and every time I step onto the pitch I do it to give 200 percent," he said.
Asked what joining Milan means to him, Diawara described the move as the fulfilment of a lifelong ambition.
"A historic club, a legendary club. Milan have San Siro, the most beautiful stadium in the world. I'm excited, I can't wait to make my debut, to meet the fans, my team-mates... I haven't fully taken it all in yet. I haven't scored a goal yet, but I'm sure the day it happens I'll carry it with me forever. When I think about what's ahead of me, it'll be incredible to share the pitch with players like that. First of all I want to settle in, then I hope to bring something to the group," he said.
He added that his footballing education began young.
"I started playing at seven, at school. I've been passionate about football since I was a child, every time I go out onto the pitch I try to give 200 percent, and little by little I'm living out my dream," Diawara said.