Chelsea will bank an initial £25.7m fee, with a further £5.1m available in add-ons after weeks of negotiation between the clubs, a package that lands close to the £30m plus £5m Chelsea had been holding out for since offers first arrived in early June.
Inter Milan had also shown interest before dropping out of the race, leaving Como as the clear favourites. Chalobah, 27, is set to sign a long-term contract in Italy and take on a leadership role under manager Cesc Fábregas, whose side secured Champions League football by finishing fourth in Serie A last season; he becomes Como's sixth summer signing, following the club's earlier business this window.
Fábregas has pushed for the move for more than six months, having crossed paths with Chalobah earlier in his career, and the defender is understood to have prioritised Italy over other options given the chance to play Champions League football with a club building around an ambitious young project.
His exit ends a stay at Stamford Bridge that began when he joined the academy at the age of eight, and will take his first-team appearance tally for the club to around 151 once his departure is formalised. Chalobah made one appearance for England at this summer's World Cup and previously spent the first half of last season on loan at Crystal Palace before an injury crisis at Chelsea forced an early recall.
The sale forms part of Chelsea's push to trim Xabi Alonso's oversized squad. The club have already brought in Maxence Lacroix from Crystal Palace for £52m, adding height and Premier League experience to the back line, which leaves them with nine senior centre-backs even before Chalobah departs: Levi Colwill, Wesley Fofana, Tosin Adarabioyo, Josh Acheampong, Benoit Badiashile, Aaron Anselmino, Axel Disasi and Mamadou Sarr.
Chelsea are also looking to offload Disasi and Badiashile before the window shuts, while Sarr or Acheampong could be sent out on loan, potentially to a fellow Premier League club. Chalobah joins a growing list of academy graduates to leave Chelsea for a fee this summer, following Andrey Santos, Tyrique George and Jimmy-Jay Morgan.