The Blues are set to receive a loan fee worth €3m (£2.5m), while Napoli’s buy option is thought to be worth €27m (£23m).
He has now been caught on camera arriving in Naples to undergo his medical and complete the move.
Footage shared by Sky Italy shows the defender in the back seat of a taxi leaving Naples airport.
Watch: Benoit Badiashile arrives in Naples ahead of Chelsea exit
He had previously been pictured on a private jet with his agent, Mounir Sidhoum.
Badiashile has not featured for Chelsea since March, when he completed the full duration of Chelsea’s FA Cup win at Wrexham, which required extra time.
It has been another summer of considerable turnover for the Blues, who have added defensive might with the signings of Maxence Lacroix, Marcos Palestra and Pep Chavarria.
He is not the first defender to depart, however, with Trevoh Chalobah completing a transfer to Napoli’s Serie A rivals Como last week.
Badiashile will hope to help Napoli close the gap to Serie A champions Inter Milan, to whom the Azzurri finished as runners-up last season. The clubs were separated by 11 points.
