Troisi, who died at 41 in 1994 a few days after wrapping his last great film Il Postino (The Postman), for which he gained two Oscar nominations, graduated in "Discipline of Music and Entertainment, History and Theory' from the University of Naples Federico II in the southern Italian port city where he started out in cabaret in the 1970s.
Troisi, who was born in nearby San Giorgio a Cremano, would have turned 70 on Sunday and a special new Rai documentary on his life and work was shown at the weekend.
Long-time friend and colleague Enzo Decaro said at the graduation ceremony: "His dad, Don Alfredo, will be happy with this degree, he was always asking us to help him in his studies.
"And today the top recognition possible has arrived".
Troisi's sister Rosaria took the parchment saying "I'm extremely moved" after arts lecturer Anna Masecchia called her brother "a complex artistic figure, rich in profundity".
Troisi moved from local theatre to TV before finding fame with Ricomincio Da Tre in 1981 playing an awkward and child-like, but very funny, Neapolitan everyman, speaking in a quirky and idiosyncratic mix of Italian and dialect.
He later acted with great director Ettore Scola before starring opposite Philippe Noiret as the Chilean poet Pablo Neruda and Maria Grazia Cucinotta as his love interest in Michael Radford's Il Postino, just days before dying from a longstanding heart defect.
"He was one of our dearest children," university dean Matteo Lorito said.
Neapolitan film director Mario Martone said "he was a Neapolitan Chaplin".
ANSA
