Osvaldo Borsani was born in 1911 in Varedo, Italy. He studied Beaux-Arts at Accademia di Brera in Milan and architecture at Politecnico di Milano, graduating in 1936. While still in school, Borsani participated in the fifth Milan Triennale, presenting his Casa Minima project, which earned him a silver medal. At the same time, he began collaborating with his father Gaetano in the family business, Atelier Varedo, producing fine cabinetry with European Deco influences. In 1932 the business was renamed Arredamento Borsani and opened its first space in Milan. Around the same time, Borsani began to collaborate with Milanese artists such as Lucio Fontana, Agenore Fabbri, Arnaldo, and Gio Pomodoro.
In 1953, Osvaldo and his twin brother, Fulgenzio opened TECNO, a firm that became known for its technology and research-based approach to furniture design. Notable TECNO designs include the 1954 D70, a sofa that can assume approximately twenty positions; the 1955 P40 chaise, featuring mobile parts with adjustable backrest and armrests; and the 1968 Graphis office furniture system, created by Borsani and Eugenio Gerli.
In 1970, together with his daughter Valeria and Marco Fantoni, Borsani introduced the Centro Progetti Tecno, a collaborative design laboratory for new product development. Borsani passed away on April 16, 1985 in Milan.