Balotelli has been linked with a summer move to Stamford Bridge, but Mourinho thinks that the Italian forward will remain at the San Siro, despite the club's disappointing form in Serie A.
The 51-year-old is quoted by Mediaset as saying: "Mario plays for one of the most important clubs in the world.
"Clarence Seedorf, however, needs time and other players to combine with Balotelli. Mario's future will be at Milan."
Balotelli has netted 27 times in 44 appearances since leaving Manchester City at the start of 2013.