The Spaniard spent eight years with Chelsea’s league rivals Arsenal before joining Barcelona in 2011. After three years with the Catalan outfit he will now return to London, but this time with the Blues.
Having finished a disappointing third last season, Mourinho will be looking for a much improved effort next season, and he expects Fabregas to play a big part in this.
“He is the kind of player we need – not just for his qualities as a player but also his competitive personality,” Mourinho told Chelsea’s official club website.
“He is a player in the best years of his career. He knows England well, he knows the Premier League well, so he will not need time to adapt.
“He is the kind of player who will come and train for a couple of weeks and be ready to prove himself.”
The 27-year-old Fabregas is currently on World Cup duty with Spain.