Alessandro Sartori was born in Trivero, in the province of Biella, the home of Zegna, and grew up in his mother's dressmaking atelier. He studied textiles in Biella and graduated in fashion design in 1989, the year he joined Zegna as a menswear designer.
In 2003 he became creative director of the new Z Zegna line, which he showed in New York from February 2007 for five seasons before moving to Milan in June 2009. On 1 July 2011 he was appointed artistic director of Berluti, with the aim of building a full luxury wardrobe; his first collection, shown at the École des Beaux-Arts in January 2012, was called "an impressive debut" by Women's Wear Daily. His last Berluti show was in January 2016.
Zegna announced his return on 5 February 2016 as artistic director of all its brands and creative functions, and he joined in June 2016. His first show was Ermenegildo Zegna Couture autumn/winter 2017 at HangarBicocca; in 2017 he opened Zegna's first Bespoke Atelier in Milan. He has staged shows at the Bramante cloister of the University of Milan, a snow-covered Bocconi auditorium, Stazione Centrale and the former Falck works. In January 2019 he launched #UseTheExisting, collections made from pre-existing materials through innovative processes, which won the Premio dei Premi for innovation in 2022. During the pandemic he presented collections as fashion films, starting with "The (Re)Set", and for spring/summer 2024 he created an "Oasi of Linen" in Piazza San Fedele with 192 Normandy flax bales.
He has designed costumes for Benjamin Millepied's dancers at the Paris Opera Ballet and the L.A. Dance Project, suits for Tilda Swinton in Luca Guadagnino's Suspiria (2018), and clothes for Genny Savastano in Gomorra. His awards include GQ Spain's best international designer (2005) and designer of the year (2015), WWD Menswear Designer of the Year and Esquire Spain's Man of the Year (2023). He collects vintage cars and Leica cameras. Casadi has not verified his date of birth.