Giancarlo Tenenti attended the Castello Sforzesco Art School, and also took courses from the Cimabue Academy. He began his professional career in the 1960s with drawing for several comic books by Editrice Cervinia, such as 'Kit del West', 'Piccolo Scout', 'Tommy Colt', 'Winchester Man, 'Doc Sullivan', 'Spectrus' and 'iccolo Scou'.
In the 1970s, he founded his own art studio in Milan, where he was joined by artists like Giovanni Freghieri and Maurizio Dotti in productions for Mondadori (Audax, Superthrilling), Edifumetto ('I Sanguinari') and Bonelli ('Zagor'). The studios' main client was, however, the publishing house Universo, for which they created hundreds of pages for Intrepido, Il Monello and Bliz. Tenenti worked on titles like 'Dark Angel' (Max Bunker Press) and 'Virtual Heroes' (Edizioni Delga) in the early 1990s. He drew six episodes of Astonia's 'Diabolik' series in 1997 and 1998.