In the Roman summer heat, Napoli and Juventus had trouble getting the game to a close, but the cup final flashed until the end of the first half.
Cristiano Ronaldo almost reached a recording and Nikola Maksimovic forced legend Gianluigi Buffon to a sweaty save.
The match went to penalty - much thanks to a phenomenal double save in the 91st minute by Buffon.
Paulo Dybala and Danilo missed Juventus first two, while captain Lorenzo Insigne and Matteo Politano were chilly for Napoli.
In the fourth round, Arkadiusz Milik got the chance to decide - and a safe side later was Napoli's Italian cup champion
The title weighs heavily on coach Gennaro Gattuso, who recently lost his sister Francesca after a period of illness.
On the other hand, Naples's old coach Maurizio Sarri, born in Naples, admitted to being defeated.