The company said on Tuesday he died overnight in his Turin home.
Pininfarina had been groomed by his father Gian Battista, a onetime Turin carriage maker who founded the influential car design house in the 1930s, to succeed him in the business since he was a child.
Born in 1926, he joined the family firm after graduating in mechanical engineering from Turin's Polytechnic University, became chief executive in 1961 and then chairman when his father died in 1966.
By then, the company had already risen to prominence through a knack for making the latest aerodynamic design trends attractive to a broader public.
The family's prestige in Italy was such that it was allowed to change its name to Pininfarina from the original Farina - Pinin, meaning "the little one" in Piedmont, was Gian Battista's nickname - with a presidential decree in 1961.
The ground-breaking 1947 Cisalfa coupe, designed by Gian Battista "Pinin" Farina after World War Two, now sits in New York's Museum of Modern Art. It was one of Sergio's favorite models.
Gian Battista also initiated the Ferrari connection in 1952, but Sergio ended up managing most of their common projects and turned the business from craftsman level into a world renowned name.