The 19-year-old Armenian international has been at Chelsea since the age of nine and has come through the youth ranks to reach this far.
He made his senior debut for Chelsea in a 4-0 Premier League win over Everton in the 2019/2020 season but that remains his only appearance.
Broja spent last season on loan in Netherlands with Vitesse, scoring 11 goals in 34 appearances across all competitions.
"I am really excited to be signing a new contract with Chelsea," Broja told the club's official website.
"Having come through the Academy here it was a special moment for me to make my first-team debut last year, before gaining further experience on loan at Vitesse last season.
"I want to build on these foundations and I am really looking forward to progressing and making an impact at Chelsea in the years to come."
It remains to be seen whether manager Thomas Tuchel will give Broja a spot in Chelsea’s first team next season or send him out on loan.
Broja made his debut for the Albania national team last year and has won six caps to date.
