Courtois is returning to Atletico for a third loan spell.
Caminero said the club had prioritised securing the services of Courtois for another year.
"The continuity of Thibaut was one of our priorities for this season," he said.
"We are very pleased to have him for another year. He has played almost every game and given us great confidence in his abilities.
"He had said he wanted to stay here so this gives everybody joy."