The defender retired from international duty last year but has re-established himself as first choice at Stamford Bridge, with Mourinho saying the 32-year-old is back to his best after making just 12 league starts under Rafa Benitez last term.
While Mourinho has not discussed the possibility of an England recall with his captain, who is keeping current England regular Gary Cahill out of the side, he is convinced Terry remains good enough to represent the Three Lions.
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"Rio Ferdinand plays for Manchester United. If he plays for Man United, he's ready for the national team.
"John Terry. When you play for a big team, you are ready for the national team.
"But the problems that ended with the player stopping to go to the national team, that's not my problem, that's not David Moyes' problem, that's not a manager's problem. It's a personal thing."
Mourinho admits he has something of a selection headache in defence, with a number of players competing for spot at centre-back, and is keen to give Cahill game time ahead of the World Cup.
"I would never do something that could jeopardise his selection for the national team," Mourinho continued.
“He is going to play a lot and who knows, in a couple of weeks I may change my mind because of performances and he becomes my first option and I leave John or David [Luiz] out.
"I have to think about Chelsea but I also have to think about them and their national teams, because it's important to them.
"When a player is not selected for the national team he is sad and when a player is sad he can't perform for Chelsea the same way he performs if he's happy.
"It's all connected. In the case of Gary, I have to make him happy, I have to make him play, he has to go to the national team and Roy [Hodgson] has to be happy."