In 2008, Ronaldinho joined Seria A giants AC Milan on a three-year contract. With the number 10 already taken by new teammate Clarence Seedorf, Ronaldinho chose 80 as his kit number.
Ronaldinho scored his first goal for Milan in a 1–0 triumphant derby victory over rivals Internazionale. He finished his first season at Milan with 10 goals from 32 appearances in all competitions. After a good start with Milan, Ronaldinho struggled with fitness and was often put on the bench of the rest of the season.
Ronaldinho own his way to score two goals against Juventus.
His second season did not begin on a good note, although he started nearly every match, he soon found himself on the bench again. Soon after, Ronaldinho rediscovered his form and was probably Milan's best player of the season. He changed his role from an attacking midfielder to a left winger. During the 2010 season, Ronaldinho scored two goals against Juventus in an away match, sealing a 3–0 victory for Milan. In the next match against Siena, Ronaldinho scored his first hat-trick for Milan when he converted a spot kick, scored with a header from a corner and finished with a wonder goal from 20 yards out.
Ronaldinho finished the season as the assists leader of Serie A. On a less positive note, Ronaldinho missed three penalties that same season. Ronaldinho ended the season scoring two goals against Juventus. LucaAntonini opened the scoring and Milan went on to win 3–0. That was Leonardo's last game in charge of AC Milan.
Ronaldinho celebrating the success of winning the Serie A.
In the 2010-2011 season Ronaldinho and Ac Milan went on to win the Seria A and became champions of Italy. They didn't even have a manager to win with. It was managed by the Head coach of the club. This was Ronaldinho's last season at the Italian club. And what a way to end his time at the great club.