The arrangement was made public on Saturday after a four-hour meeting between Berlusconi and vice-president and current general manager Galliani the previous night.
Berlusconi says "Galliani will take charge of the sporting sector, while Barbara Berlusconi will manage the other sectors."
Galliani had said he would resign on Friday after clashes with Barbara Berlusconi, a member of the board of directors.
Earlier on Saturday, Berlusconi told Italian news agency ANSA "calm has been restored to Milan. Adriano Galliani is staying in his job."
Galliani has held the role for 27 years.