The goalkeeper has been in outstanding form for Atletico Madrid this season, but he feared he would miss out on the biggest occasion of his career when the Spaniards drew Chelsea in the last four.
Reports suggested that the 21-year-old, who has been on loan with Atletico for the last three seasons, would be given permission to play if the La Liga leaders paid Chelsea a substantial fee.
But the speculation has been dismissed by UEFA, who cleared Courtois to feature without the need for any money to change hands.
"I was very relieved," Courtois told the FIFA website. "For me, the fact that we've drawn Chelsea, like we did in the European Super Cup in 2012, is special, because even though I'm at Atleti, Chelsea are my club too.
"It's better not to think about it too much though and play like I always do, because if I start thinking, 'Oh, I'd better be careful', then I'll end up playing poorly.
"I want to win trophies here and I'll be an Atleti supporter for these two games, but at all other times I'm a Chelsea fan too.
"I hope they win the Premier League, just not these two Champions League matches. I really hope we can reach the final as we're so close. They're the favourites, but Barcelona were too."
The first leg of the tie will be played in Madrid on Tuesday, with the return at Stamford Bridge next week.
Courtois has already lifted the Europa League, UEFA Super Cup and Copa del Rey in his three seasons on loan in Madrid, and admits he never expected so much success when he first made the move.
"I didn't expect it, no," he added. "I remember playing my first game in the Belgian league just before turning 17 and dreaming of having a good career over there, but I didn't imagine playing for a big club or winning trophies like these.
"And now we're not far away from the most important one of them all, the Champions League.
"We've got the Liga title close too which, because of Barcelona and Real Madrid, you never think you'll get the chance to win.
"They've got better individuals but we're a very good team and that's important, because you don't need to rely on any one player to win the championship.
"It's going to be hard to repeat all this though. We're having a huge season and, now we've got this far, we've got to try and take advantage.
"It'll be tough to take if it ends without us winning anything, but it won't be for lack of trying."