The goalkeeper has welcomed the opportunity to work with the Portuguese again, describing his return as something he had been looking forward to.
Courtois worked under Mourinho at Chelsea and has now been reunited with the manager at Real Madrid. Speaking to Sky Sports at the Web Summit in Lisbon, the Belgian reflected on the differences between the coach he remembers from 12 years ago and the one he has encountered in the current Madrid dressing room.
"It's always good to work with him again. He is an excellent coach, and I was looking forward to his return," Courtois said.
The goalkeeper believes Mourinho has become more measured with experience, although he retains the demanding character that has been a defining feature of his management throughout his career.
"I remember that at Chelsea Mourinho was more assertive in the dressing room and conveyed a stronger sense of pressure. He is still like that now, but compared with my memory of him 12 years ago, I think he is slightly less intense," he explained.
Courtois suggested that Mourinho himself has acknowledged the changes in his approach, with the experience accumulated over the years helping him become calmer in certain situations.
"I will use his own words. I think he himself has said that he may have matured a little. With all that experience, I think he is also a little calmer at times," the goalkeeper said.
However, Courtois insisted that the manager's personality and ability to command attention remain unchanged. He believes Mourinho still has a distinctive presence that can be felt throughout a room, something he considers valuable within a dressing room.
"His personality is still the same, and his presence is still the same. You walk into a room and, while he is there, you can feel his presence. I think that is exactly what we need," he said.
Courtois also revealed an amusing detail about the beginning of their reunion. Mourinho sent him a message when he arrived at Madrid, but the goalkeeper did not respond for two weeks because he had missed it while travelling with Belgium.
"I remember accidentally ignoring his first message for two weeks. We were at the World Cup at the time, and on the day he sent it, we were on a plane. The time difference and the lack of Wi-Fi on the flight meant I missed a lot of messages," Courtois explained.
He eventually received another message after a match and had to check with someone at the club that the number belonged to his new manager.
"After a match, he sent me another message, and I asked someone at Real Madrid: 'Is this the coach's number?' But everything is fine now," he added.
Courtois also discussed Xabi Alonso's time at Real Madrid, saying he liked the former coach's methods and believed he would eventually achieve good results at Chelsea. He felt Alonso's departure from Madrid had been harsh, arguing that managers are often the first to pay the price when results deteriorate.
But it was his assessment of Mourinho that offered the clearest insight into the current relationship. Courtois believes the manager has evolved without losing the authority and personality that made such an impression during their first spell together.