The 24-year-old, who only recently moved back to Roma from Genoa after the capital club bought out his co-ownership agreement, has signed a four-year deal at the San Siro.
Bertolacci played 34 times in Serie A for Genoa last season, scoring six goals, and he said it is a move he has long targeted.
“I have always said to CEO Adriano Galliani that I wanted to come here and it’s a great feeling to see it happen,??? he told the club???s official website.
???I’m ready to prove myself.
“It was always my first choice to come here. Galliani showed great enthusiasm to sign me. Now it will be up to us on the pitch to show we can win the Scudetto.
“I spoke on the phone with new coach Sinisa Mihajlovic and he has a great desire to bring back a Milan side of true greatness.
“I have excellent confidence after last season and at Milan I already have great friends. It’s really good to be here.”