Coming into the contest on a three-game unbeaten run across all competitions (W2, D1), Milan made a confident start against La Dea.
The hosts dominated possession early on, and they thought they’d broken the deadlock in the 13th minute, only for Christian Pulisic’s emphatic close-range finish to be ruled out for a marginal offside. Atalanta threatened a breakthrough themselves shortly after, with Nikola Krstovic rounding Mike Maignan and firing wastefully into the side-netting.
Keen to make the most of that reprieve, Ruben Amorim’s men were awarded a penalty in the 24th minute, when Yunus Musah’s effort was blocked by the hand of substitute Relja Obric.
Goncalo Ramos stepped up to the spot for the Rossoneri, and the Portuguese forward sent Marco Carnesecchi the wrong way to score his second league goal of the season.
Having lost their last two Serie A trips, La Dea pushed for a response before half-time, but it was Milan who doubled their lead in the 43rd minute.
Diego Moreira picked out Adrien Rabiot in the box, and the Frenchman cut inside one defender before stroking a composed finish into the bottom corner.
The hosts looked to extend their advantage further at the start of the second period, with Samuel Chukwueze curling narrowly wide, while at the other end, Krstovic skewed a difficult chance off target.
Milan were awarded their second penalty of the evening in the 56th minute after a handball from Thomas Kristensen, but Ramos’ spot-kick was expertly thwarted by Carnesecchi.
That proved to be a momentary reprieve for the visitors, though, as the Rossoneri found the net just a minute later, with Mario Gila heading home at the back post after a clever flick-on from Rabiot.
La Dea responded by pulling a goal back through Gianluca Gaetano’s superb touch and finish in the box, setting up a nervy final 20 minutes at San Siro.
That tension was amplified with nine minutes remaining, when Raoul Bellanova’s cutback was clinically swept into the bottom corner by Krstovic.
Armed with all the momentum, Atalanta nearly completed a remarkable comeback two minutes later, but Maignan came to Milan’s rescue to deny substitute Davide Zappacosta.
The visitors’ pressure continued deep into stoppage time, but Milan ultimately held firm to earn a first head-to-head league victory in seven meetings.
Flashscore Man of the Match: Adrien Rabiot (AC Milan)