The Portuguese head coach, who in 2014-2015 led the Blues to their first English Premier League title in five years, began his second stint at Stamford Bridge in June 2013, reports Efe.
In his first tenure from 2004 to 2007, the 52-year-old Mourinho led Chelsea to two league championships, one FA Cup crown and a pair of Football League Cups, a knockout competition involving teams from England and Wales.
The announcement comes a day before Chelsea kicks off its title defence with a home match against Swansea City.
“I said when I returned here two years ago that I have a special feeling for this club and nothing changed. It is the club closest to my heart and I am very happy to know I will be staying here for a long time,” said Mourinho said Friday, who won Champions League titles with Porto and Inter Milan and also has coached Real Madrid.
“If the club is happy, I am happy. I think this is a normal thing for me to sign a new contract. It is important we have this continuity and I hope we can enjoy more success in the future – for the fans, the players and the club,” Mourinho, who signed an initial four-year deal in 2013, added.
Besides last season’s league title, Chelsea also won the 2014-2015 Football League Cup with a 2-0 victory over Tottenham in the final.
In announcing the contract extension, Chelsea noted that Mourinho’s 70 percent win rate is better than any other head coach in the English Premier League history.
It also recalled that the 95 points the Blues recorded in Mourinho’s first season (2004-2005) still stands as a league record.
“We are very happy that Jose has committed four more years to the club,” Chelsea director Marina Granovskaia said.
“Since his arrival two years ago, he has carefully developed the playing squad and brought trophies to Stamford Bridge. We look forward to the next four years and the continued success of the team.”