Bellini began his career working as an architect and designer for companies such as Olivetti, Cassina, B&B Italia and Vitra. He is known for his innovative furniture designs, which often feature unique sculptural shapes and materials.

Some of Bellini's most famous works include the "Cab" chair (1977) for Cassina, the "Le Dolls" sofa (1972) for B&B Italia, and the "Camaleonda" modular sofa (1971) also for B&B Italia. He has also designed products in a variety of other categories, including lighting, office equipment and home accessories.

In addition to his work in design, Bellini was also involved in architecture. He has designed buildings such as the National Gallery of Victoria in Melbourne, Australia and the Tokyo Design Center in Japan.

Bellini has won numerous awards throughout his career, including eight Compasso d'Oro awards, one of the most prestigious awards in the design industry. He has also been recognized as a Royal Designer for Industry by the Royal Society of Arts in London and was inducted into the Interior Design Hall of Fame in 2011.