Courtois will once again be available for Chelsea, as they take on Bournemouth come Saturday.
Courtois has been out for three months with a knee injury, but according to Mourinho, he could make a return soon.
“Thibaut was our keeper all last season and you know how fundamental he was. It’s important to have him back,” Mourinho told a media conference.
Asked whether he would start, Mourinho added: “I’ve not told them [the players] so they must know first but he’s in the group.
“He’s has been out a long, long time, too long. So now we feel better. We have [Asmir] Begovic and Marco Amelia and now we are safe.”
There was less positive news elsewhere on the injury front for Chelsea with John Terry, Ramires and Radamel Falcao all absent for the clash with a Bournemouth side sitting in the relegation zone.
Mourinho now has a choice to make with Begovic impressing in Courtois’ absence despite Chelsea’s poor start to the season.
“Courtois is Courtois,” the manager said. “To lose him for a few matches [is tough] but we knew we had good protection.
“Nineteen matches without the best goalkeeper in the world was hard for us but now we are in a good situation. The best and very good.”