Entered in the ecclesiastic career, he moved to Rome where he was appointed auditor (judge) of the Roman Rota.

In 1580 Pope Gregory XIII appointed Visconti as own legate to investigate and to settle a dispute in the Order of Malta about the contested deposition of the Grand Master Jean de la Cassière.

Returned in Italy from Malta in 1583, on 4 November 1584 Visconti was appointed bishop of Novara, as advised by Saint Charles Borromeo to the pope.

[4] During his tenure as archbishop many religious institutes opened their convents in the archdiocese, such as the Camaldoleses in 1590 and the Camillians in 1594.

[4] Following the footsteps of Charles Borromeo, Visconti convened six diocesan synods, started the pastoral visit to all the diocese, erected new churches such as Santa Maria al Paradiso in Milan and the church of Montevecchia and established the hospital of Fatebenefratelli in Milan.