Courtois picked up an ACL injury last August, just before Real Madrid's opening match of the season against Athletic Bilbao, before suffering another knee issue in March.
At the time, it had been feared that the Belgian would miss the rest of the season, but he has made a fast recovery from his second operation, and the stopper started against Cadiz on Saturday.
The 31-year-old produced a clean sheet in his side's 3-0 win, with Brahim Diaz, Jude Bellingham and Joselu on the scoresheet for Carlo Ancelotti's side at Bernabeu.
Real Madrid will be confirmed as La Liga champions for the 2023-24 campaign if second-placed Barcelona fail to overcome third-placed Girona this evening.
Thibaut Courtois secures clean sheet in first game of season
"A very nice day. Very happy to be able to feel like a goalkeeper again and with the victory. We are close to winning the league," Courtois told reporters after the clash with Cadiz.
"At first I thought I won't play this season, then I set a goal, but I got injured again, and in the end I was able to come back.
"On Wednesday (against Bayern Munich in the Champions League) we have another very important game and we hope that with the fans and everyone in white we can give another joy.
"It will take a little time to adapt again. The plan was to play a friendly match in training at the time, but I tore my meniscus. I only trained, but I haven't played 11 vs. 11 for nine months.
Real Madrid in good shape ahead of Bayern Munich clash
"We are a group of friends in the team. A hug and a positive word always helps a lot. [Eder] Militao and I spent several days alone at the time of our injury. Playing with him again means a lot to me. I would like to thank the technical staff very much. I am better now."
Real Madrid will welcome Bayern to Bernabeu on Wednesday evening for the second leg of their Champions League semi-final, with the tie level at 2-2 following the first leg in Germany.
Los Blancos did not suffer any fitness issues against Cadiz, meaning that David Alaba is set to their only absentee for the clash with Thomas Tuchel's side.
There had been some concern over a foot problem for Aurelien Tchouameni, but the midfielder was in the squad on Saturday afternoon and was ultimately an unused substitute.
Toni Kroos, Rodrygo, Ferland Mendy and Antonio Rudiger were also among those rested, but Bellingham, Vinicius Junior and Federico Valverde did feature off the bench.