As reported on Monday, the experienced team defender is finishing his career as a footballer this season and is ready to become assistant to coach Carlo Ancelotti.
In addition to A. Costacurta, who made his debut at AC Milan in 1986, former striker Leonardo will also return to the team's technical staff.
"At Carlo's advice, Costacurta will take over the duties of the second assistant coach alongside Mauro Tassotti. Also, starting from July 1, Leonardo will return to the team's board," said vice president Adriano Galliani, as quoted on the Milan club's website.
Another member of the solid age group of Milan defenders, Brazilian Cafu, has extended his contract for another season, while the future of Paolo Maldini is uncertain.
The 38-year-old Italian declared at the beginning of the season that he would most likely end his career after this season, but later spoke about his desire to play for another year. With just over two weeks left until the Champions League final, the footballer is dealing with a knee injury.