The 42-year-old declares himself is content with his current options between the sticks amid speculation that he could be ready to offer the Real Madrid star first-team football
The Spain international, 32, lost his starting berth to Diego Lopez under Jose Mourinho last term and has been unable to win back his slot since Carlo Ancelotti took charge at the Santiago Bernabeu.
Casillas's struggles have prompted speculation that he could seek a move away from los Blancos in an effort to maintain his position with la Roja ahead of next summer's World Cup.
Atleti, as well as Arsenal, have reportedly been monitoring his situation but Simeone says that Chelsea youngster Thibaut Courtois - who is on loan at the club for a third consecutive season - is his No.1.
"Courtois is our goalie," he told reporters. "We also have two other goalkeepers waiting for their chance so no, we wouldn't be interested in Iker Casillas."
Los Rojiblancos face Barcelona in the second leg of the Supercopa on Wednesday, which kicks off at 22.00BST.