A painter, draughtsman and  art theorist, as a youth Paggi was influenced by Cambiaso, but because he killed a man during a quarrel, he was banished from Genoa in 1579 and took refuge in Tuscany. In Florence Paggi gained reputation at the Medici court and joined the Accademia Fiorentina delle Arti del Disegno in 1586. He shared a studio in Florence with Federico Zuccari. Paggi returned to Genoa as early as 1590, but not permanently till 1599, under the protection of the Doria family. In a short time his paintings and drawings, which combine sfumato, the delicate coloration of Tuscany, with geometric elements from Cambiaso, made him the leader of the Genoese school. Paggi's treatise, Definitione e Divisione della Pittura, published in 1607, and his letters to his brother in Genoa attack the old guild laws and urge  for new reforms. He was the teacher of Giulio Benso, Giovanni Benedetto Castiglione, Sinibaldo Scorza, Domenico Fiasella, and Giovanni Andrea Podestà. Other sources cite Scorza, Luciano Borzone, Giulio Benso Bernardo Castello, Giovanni Domenico Cappellino, Agostino and Giovanni Battista Montanari as his pupils.