[1] Born in Le Nouvion-en-Thiérache on 15 June 1932, Fainsilber graduated from the Beaux-Arts de Paris in 1960 and subsequently worked for Hideo Sasaki in Watertown, Massachusetts.
Upon his return to France, he became director of studies at the Institut d'aménagement et d'urbanisme de la région d'Ile-de-France [fr] and participated in the first Schéma directeur de la région Île-de-France [fr].
In 1970, Fainsilber founded his own architectural agency after winning the Villetaneuse campus competition alongside Högna Sigurðardóttir.
In 1980, he was selected for a competition at the Cité des Sciences et de l'Industrie by President Valéry Giscard d'Estaing,[2] then for one at La Géode.
[3][4] In 1992, Fainsilber founded a single member limited liability company [fr], of which he was the sole manager and partner.