Belotti began his academic path in 1938 when he at the age of 16 took a sculpture course at the Instituto Superiore per le Industri Artistische (ISIA) in Monza. In 1941 he enrolled in the architecture course at the Politecnico di Milano.
Beginning in 1949, Belotti worked in the Milan offices of Franco Scolari, Giulio Minoletti, and Guglielmo Ulrich. In 1954 he joined Achille Boraschi, Sergio Invernizzi, and Vittori Korach in subscribing to the manifesto of the Architettura Contemporanea movement. In 1960 Belotti founded his own architect studio in Milan. Here, he developed his first independent projects as a building and interior architect, in collaboration with Sergio Invernizzi.
During the end of the 50’s, Belotti studied architecture at the Architettura di Venezia (IUAV), from where he graduated in 1961, and it is during the 60’s that Belotti got his real breakthrough. Belotti’s career as an architect started with the Albergo Marina in Marina di Massa (1961/62), the Lactis milk factory in Albano Sant’Alessandro (1961-64) and a building for Serio Futter-mittel food producer in Riviera d’Adda (1965-67).
As a furniture designer Belotti’s debut came with the iconic Spaghetti chair, with steel tube frame and PVC strings, designed in 1962 to the Albergo Marina. Later the Spaghetti chair was the start of the collaboration between Belotti and the manufacturer Alias who re-launched the model in 1979. Their cooperation continued during the 80’s with pieces such as Paulis chair and the Outdoor furniture collection (both in 1983).
In 1984 Belotti became the leader of the Laboratorio di Urbanistica, Architecttura e Disegno Industriale at the SCP (Società Cooperativa di Progettazione) in Genoa, that developed design and architectural projects in Africa and Central America. Five years later the project moved to Sarzana and was re-named Labororatorio di architettura Belotti Associati.
In 1992 he started to work with Foppapedretti, for which Belotti made the Plein Air furniture collection (1996). Giandomenico Belotti died in 2004 at the age of 82.