Charles was the son of Count Gilbert Borromeo and Margaret Medici, sister of Pope Pius IV. In 1559 his uncle was elected Pope Pius IV and the following year, named him his Secretary of State and created him a cardinal and administrator of the see of Milan. He served as Pius’ legate on numerous diplomatic missions and in 1562, was instrumental in having Pius reconvene the Council of Trent, which had been suspended in 1552.

In his later work he gave priority to the needy and increased the systems to the poor. He was most generous in his help to the English college at Douai, and during his bishopric held eleven diocesan synods and six provincial councils. He founded a society of secular priests, Oblates of St. Ambrose (now Oblates of St. Charles). He died at Milan on the night of November 3-4, and was canonized in 1610. He is patron of learning and the arts.