The move is significant because until now in his career, the Portuguese coach has never spent longer than three seasons at any one club.
If he completes this season at Stamford Bridge, he will have matched his own personal record, while his new contract signing indicates that he is keen on surpassing his previous ‘longest-ever stint’ at a club.
The new deal was announced on Chelsea’s official website, and will keep the manager in west London until 2019 at the earliest.
Mourinho twice won the Premier League during his first spell with the Pensioners—between 2004 and 2007—while also winning the FA Cup and two League Cup titles.
He achieved a record 95-point tally in 2004/05, but departed as relations became strained with club chief Roman Abramovich.
Since returning in 2013, he won both the League Cup and the EPL title last term.
“If the club is happy, I am happy,” Mourinho began, discussing his new contract with ChelseaFC.com.
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“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.
“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.”