Chelsea paid close to £30m to acquire the services of the ex-Arsenal captain, who spent eight years with their north London rivals.
And Mourinho believes his experience of the Premier League will stand him in good stead when he joins up with Chelsea's squad.
“He is the kind of player we need,” the Portuguese told ITV. “Not just for his qualities as a player but also his competitive personality.
“He is a player in the best years of his career – 26, 27, 28. He knows England well, he knows the Premiership well, so he will not need time to adapt.
“I think he is the kind of player who will come and train for a couple of weeks and be ready to prove himself.”
Fabregas is likely to replace Frank Lampard in the Chelsea starting XI, with the England midfielder set to leave the club after the World Cup in Brazil.
New York City are reportedly the frontrunners to sign the 36-year-old, with QPR also credited with an interest.