The 18-year-old joined Chelsea from Premier League rivals West Brom in 2013.
Brown is currently on loan at Vitesse Arnhem.
Brown wrote on his Twitter account: “Very happy to have a signed a new 4 year contract with @ChelseaFC, hard work doesn’t stop!”
Izzy Brown has today signed a new four-year contract… http://t.co/7ecJqTJDwC pic.twitter.com/I8hZLapGqd
— Chelsea FC (@ChelseaFC) September 1, 2015
