Milan climbed into Serie A's top four as Junior Messias secured a 1-0 win at Monza, whose owner Silvio Berlusconi failed to get one over on his old club.
Messias fired home on the turn just after the half-hour mark after Monza – who entered the game as Serie A's only unbeaten team in 2023 – twice went close in a fast start to Saturday's match.
Monza played their part in a lively affair but were unable to give Berlusconi – who bankrolled Milan to five European crowns – a result to cherish against his beloved Rossoneri.
Milan were able to claim victory without calling on Zlatan Ibrahimovic for the first time this season, with the striker again an unused substitute as they moved above Atalanta and Roma into third place.
Ciprian Tatarusanu was forced into action twice in the first two minutes, turning Patrick Ciurria's attempt away at the near post before denying Andrea Petagna from the resulting corner.
Rafael Leao saw a dipping 25-yard strike brush the post as Milan played their way into the game, while Michele Di Gregorio made two sharp saves to keep out Brahim Diaz and Fikayo Tomori.
Di Gregorio was finally beaten 31 minutes in, however, getting a hand to Messias' powerful left-footed volley but failing to stop the ball from finding the bottom-right corner.
Ciurria drilled a 20-yard effort against the foot of the post with 17 minutes remaining, but Milan stood firm and almost added a second through Charles De Ketelaere.