Milan were desperate for a return to winning way dropping points in their last two league encounters.
The hosts broke the deadlock after just 13 minutes when Cagliari's Luca Ceppitelli turned the ball into his own net on the rebound after Suso's initial strike was saved.
Milan double their advantage in the 22nd minute as Davide Calabria sent a superb ball into the box, where Lucas Paqueta was on hand to nod home.
Cagliari managed to see a bit more of the ball as the first half went on, while Joao Pedro did well to force Gianluigi Donnarumma into a fine save with a close-range header.
The home side came out firing in the second half, which saw them rewarded with a third goal on 65 minutes as Krzysztof Piatek grabbed his fourth goal in three games with a close-range finish.
Suso went close to adding his name on the scoresheet with ten minutes remaining after finding space in the box, but the Spaniard sent his effort inches wide of the upright.
Gennaro Gattuso's charges managed to see out the remaining stages of the half to claim three points, which sees them move from seventh to fourth spot.