The occasion was overshadowed by the death this week of Sevilla midfielder Antonio Puerta, who collapsed during his side's first league game of the season last Saturday.
The Italians prevailed in the curtain-raiser to the continental club season courtesy of second half goals from Filippo Inzaghi, Marek Jankulovski and Kaka.
UEFA Cup winners Sevilla, who won the trophy last year when they thrashed Barcelona 3-0, had opened the scoring through Brazilian striker Renato.
The players, who were wearing black armbands and had Puerta's name at the bottom of their shirts, paid tribute to the player with a minute's silence.
Spanish football, and Sevilla in particular, has been stunned by the death of the versatile left-sided player.
Puerta died on Tuesday in a Sevilla hospital at the age of 22. Sevilla substitutes and members of staff were wearing his number 16 shirt.
PUERTA BANNERS
"Puerta presente" (Puerta, you are with us), "Puerta no te olvidamos" (Puerta, we will not forget you), read banners in the Sevilla fans' corner.
"Onore a Puerta" (glory to Puerta), said a banner in the Milan fans' stands. The banner was presented to the Sevilla fans at halftime.
Fans from both teams chanted his name during the warm-up, with the Andulasians warmly applauding their Milan counterparts.
Sevilla were the first in action and Renato opened the scoring when he headed home from a corner kick after 15 minutes. All players regrouped and raised their arms towards the sky.
Ten minutes later, the Brazilian striker met a Frederic Kanoute cross from the right but Alessandro Nesta saved on his goal line.
Inzaghi had a goal disallowed for AC Milan on the stroke of halftime for an offside position.
However, the striker levelled the tie on 56 minutes when he beat Andres Palop with a header from a Gennaro Gattuso cross.
Czech left back Marek Jankulovski doubled the tally six minutes later with a powerful volley from the edge of the box.
Brazil's Kaka made it three for Milan when he headed home three minutes from time after Palop had parried away his penalty kick.