The former Fulham shot-stopper has turned down Aston Villa and agreed a two-year deal with the Tuchel side.
Bettinelli will arrive as a free agent, after his contract at Craven Cottage expired.
He is due to complete his medical and sign for the club in the next 48 hours.
Chelsea manager, Thomas Tuchel has been searching for a new goalkeeper after Willy Caballero’s departure last month.
Bettinelli will offer back-up to first choice Edouard Mendy and competition for No 2 Kepa Arrizabalaga.