Cech joined the club from Rennes in 2004, and has since won 12 major titles including three Premier Leagues and one UEFA Champions League crown.
This season has seen Cech usurped as Chelsea's regular number one by Thibaut Courtois, with the former only making five league appearances so far in 2014-15.
And speculation has been rife that the Czech Republic international will move away from Stamford Bridge at the end of the season.
"He will make his decision," Mourinho said. "He's very mature to make what he feels is the best decision for him and the best decision for his future.
"I will just wait. I would like him very much to stay. I don't waste my time trying to persuade him, because I know nobody can persuade him.
"If he tells me he wants to leave, I will tell him my opinion and my opinion is [that Cech is] one of the three best goalkeepers in the world. Huge money."
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