The 30-year old has been linked with moves to Corinthians and New York Red Bulls, but the Madrid coach said he wanted the former AC Milan forward to stay in the Spanish capital.
"I don't think we'll do anything in January, and I don't think Kaka will leave either," Mourinho told a press conference.
|LA LIGA PREVIEW
|Barcelona aim to win for Tito Vilanova, while Real Madrid travel to Malaga
"If he stays it's good for the team," he added.
Mourinho also took the time to speak about Uefa's recent decision to fine and ban Saturday's La Liga opponents Malaga.
The Andalusians have been excluded from the next Uefa club competition for which they qualify, and could face further sanctions after failing to meet financial requirements.
"I hope that the terms are given so that it is sorted out. If they earn [European qualification] on the pitch it would be sad that, for non-sporting reasons, they could not do it. It would be sad for the fans," he said.
The former Inter coach also expressed his support for Barcelona boss Tito Vilanova, who has recently fallen ill.
"What I do in private, I do not say publicly. If I have talked to him [Vilanova] or sent him a message, it's personal. When a fellow coach has a health problem, we are all on the same side. For Tito and his family, we are with them."
Los Blancos currently lie third in the Liga table after amassing 33 points from their opening 16 games, and travel to face fourth-placed Malaga, who are just five points behind Mourinho's men. Kick off is 20:00CET on Saturday.