A clerk in a Milanese bank until he was twenty, he started taking evening classes at the Brera Academy in 1947, and enrolled for the Academy’s regular courses three years later. He studied painting under Aldo Carpi and engraving with Benvenuto Disertori, graduating in 1954. In the second half of the 1950s he took part in the group exhibitions of the artists who belonged to the Realismo Esistenziale movement, becoming one of its undisputed protagonists. Through the American gallerist Charles Feingarten, he organized solo exhibitions in Chicago (1955, 1956, 1958, 1959), San Francisco (1959) and New York (1960); he also displayed his works at the Venice Biennale in 1960, 1964 and 1972. Shortly after Guerreschi’s death, Renato Barilli devoted a retrospective to the artist, which opened in December 1986 at the Rotonda di Via Besana, Milan.