After growing up in the A.C. Milan youth system, Maiolo was promoted to the senior side under manager Fabio Capello, and later made his professional debut and only appearance for the club in the Coppa Italia the following season, on 23 October 1996, in a 2–0 away win over Reggiana; however, he did not make a single league appearance for the club during the 1996–97 season.