The 25-year-old central-midfielder joined Tottenham from Lyon in the summer of 2019 for a club record transfer fee worth €62m.
The French midfielder is considered surplus to requirements by manager Antonio Conte and has trained separately from the rest of the squad this season.
Fulham and Everton were interested in acquiring the services of Ndombele this season, but the midfielder rejected their approaches.
Napoli were keen on signing the player and the Serie A giants held discussions with Tottenham to sign Ndombele on a season-long loan.
And Ndombele is currently undergoing a medical at Napoli before finalising his move to the Serie A club.
The French international is expected to sign a season-long loan agreement with the Italian team.
Ndombele spent the latter half of the last season on loan at Lyon and made 15 outings for the French outfit, scoring once and providing two assists.
