The Belgian international is completing his move from Genk, and was expected to stay with his current club for the forthcoming season.
However, it has now emerged that he will move to La Liga where he is likely to replace David De Gea, who joined Manchester United earlier this summer.
"It is better for me to go to Atletico, I can learn more in Spain than in Belgium," said Courtois.
"I could be loaned out for a second or even third season before becoming part of Chelsea's first-team squad."
Courtois said that Chelsea's players made him feel welcome when he was shown around Stamford Bridge.
"I was already presented to the players. Lampard and Terry immediately talked to me, and Drogba said he saw on TV how I celebrated the title with Genk, and goalkeeper Petr Cech and I exchanged a few words," he explained.
Atletico had wanted to sign Courtois permanently before Chelsea captured the 19-year-old.