Real Madrid won 2-1, with Jacobo Ramon grabbing an injury-time winner.
Afterwards, Courtois said: “I wish the number was higher but I missed out on some games with the injury last year. It's an honour for me to reach this milestone.
"I dreamed of being the Real Madrid goalkeeper ever since I was a kid. It's amazing to get to this figure in LaLiga, and to have won so many trophies.
"This hasn't been the best season in terms of titles but we're still working hard. I'm excited to keep playing in this crest for many more games to come."
Madridistas can be proud of young players
On Jacobo, the Belgian also said: “Jacobo is a lovely guy, a real good lad. He was unfortunate with the two games he played against Leganés and Celta.
"He's kept working hard and I thought he looked comfortable and confident out there today. He did a great job, he came close a few times throughout the game.
"To see him score like that right at the end is amazing for the academy. There are lots of kids knocking at the door and when they're called upon, they deliver, like Raúl, Jacobo, Gonzalo, Víctor Muñoz. As Madridistas, we should be immensely proud of our academy and keep believing in them.”
Club World Cup our goal
Courtois admits the focus will soon turn to the Club World Cup, with Barcelona remaining comfortable at the top of the LaLiga table.
He added, "Physically I feel good, I'm working hard to finish the season as strongly as possible and be in top shape for the Club World Cup, which is another goal of ours. We're heading into it with a real desire to win.
"It's the first edition and if you can win it, as Real Madrid, the best club in the world, then we have to give it our best."