The 50-year-old has penned a four-year deal at Stamford Bridge and, in a brief message to Blues fans, promised to work hard to make the club successful, just as he did in 2004
Mourinho signed a four-year deal with the Blues after two seasons at Inter and three at Real Madrid, and will be officially unveiled to the media in a week on June 10.
But he delivered a short message to Chelsea supporters via the club's official website, in which he echoed the pledge he made nine years ago to give quality, work, passion and love to make the Blues successful.
"It's exactly the same message but now I can say I'm one of you and that makes a little bit of a difference," he said. "In my football career I had two great passions; Inter and Chelsea. And Chelsea is more than important for me.
"It was very, very hard to play against Chelsea and I did it only twice [while at Inter in the Champions League], which was not so bad. So I promise exactly the same things I promised in 2004. The only difference to have is that I'm one of you."
Mourinho revealed that he decided to rejoin Chelsea just "a couple of minutes" after meeting owner Roman Abramovich.
"I'm very happy," he added. "I had to prepare myself to not be too emotional at my arrival at the club but obviously I’m very happy. It was an easy decision.
"I met the boss, the owner and I think in five minutes, after a couple of very short but pragmatic questions we decided straight away. I asked the boss 'do you want me back?' and the boss asked me 'do you want to come back?' and I think in a couple of minutes a decision was made."