The Portuguese coach said he will be back in the squad ''by mid-January.''
Kaka trained with the rest of the squad on Saturday for the first time since undergoing surgery on his left knee on Aug. 5.
''Today was a basic training session, at low intensity and with zero risk for him,'' said Mourinho. ''(Kaka) incorporated himself into the group and felt like a player again.''
The former European Footballer of the Year had an operation on the same knee in 2008 and missed the first part of the 2008-2009 season with AC Milan due to swelling.
Kaka joined Real Madrid in 2009 and scored eight goals in 33 appearances last season.
Mourinho, speaking ahead of Sunday's match against Sevilla, said he considered 2010 to have been the best year of his career.
''From one to 10, I would give myself an 11, because I won all the competitions that I could with Inter and at this stage with Madrid we have the possibility to win all the competitions. It is a perfect season,'' he said.
Mourinho guided Inter Milan to the Champions League, Italian league and Italian cup titles last season.