Callejon joined Real in the summer from Espanyol, having come through the junior system at the Madrid giants.
Mourinho said: "Callejon spent two years away from Real Madrid and knows what it's like to play here and for another team. He may value what it means to be here more than other players and every minute he spends on the pitch is important to him.
"For some players it's a problem to come out from the bench for just ten minutes, but he thinks it's fantastic to do so. He respects his teammates and they respect him in turn. I like his mentality and he is, without a doubt, a player for Real Madrid."