Additional investment in the 110-year-old club would help the family's Fininvest holding to shoulder growing spending needed to support Monza, the people said, asking not to be named as discussions are private.
Fininvest is working with banks to tap international investor interest in the asset, the sources said, in what would be the latest in a number of deals in Italian soccer involving foreign investors.
Former Italian Prime Minister Silvio Berlusconi, who previously owned AC Milan, took over Monza in 2018 when it was playing in Italy's third-tier in a deal reportedly worth just 3 million euros.
Led by former AC Milan boss Adriano Galliani, Monza, a city just north of Milan, secured its first Serie A promotion last year and are currently 11th in the league standings.
However, since the Fininvest takeover, the club has accumulated losses of over 70 million euros ($74.3 million), with the tally set to rise further, driven up by investments to enable the squad to compete in Italy's top league.
The potential stake sale was first reported by Italian newspaper Corriere della Sera.
