The Belgium international is on loan at the Vicente Calderon for a third successive season after deciding he would not be guaranteed first-team football ahead of long-term No.1 Petr Cech.
No decision has yet been made regarding next season, but Courtois has called Atletico "the most important club of my life".
|4/9||Chelsea are 4/9 with Coral to finish as the top-placed London club|
"This year I wanted to stay at Atletico because I wasn't sure if I would play at Chelsea. Besides, I was excited to play in the Champions League with Atletico and wanted to be a starter with a view towards the World Cup.
"But now everything depends on Chelsea. I had a conversation with [Jose] Mourinho and decided it was best to stay here. I belong to Chelsea, but Atletico are the most important club of my life. I've got titles and prestige in a short time."
Atletico sit second in La Liga following a superb start to the season, but Courtois knows Diego Simeone's side have a long way to go if they are to be in the running for the title along with Barcelona and Real Madrid.
He added: "We are working very hard for the team to maintain this level all season, but the road is very long. We want to get as far as possible and we are showing that we have the team for it.
"It has improved a lot since Simeone arrived. He is one of the best coaches in the world, he's well motivated and gets the best out of everyone. He has instilled his winning mentality."