The Rossoneri won a sixth straight Serie A and third successive title after beating Fiorenteri 6-1 at Stadio San Siro.
Juventus, who had lost their previous three matches in the league, were in first place in the table after they beat Fioreno in Turin.
Milan, who have not beaten a Fiorenon since 1993, had lost 3-1 to Roma in the opening game of the season.
Roma had won their previous four league games, but lost to Juventus in Rome and lost 3:2 at Stadiuto San Sibyl.
Juve were without goalkeeper Antonio Conte, who was taken off after 15 minutes due to injury.
Conte is still nursing a shoulder injury but has returned to training with his team-mates.
Juarez have won their last five Serie A games, and their last two games have been decided by two goals.