The 2012 Olympics in London were Van Rouwendaal's first Olympics. She competed individually in the 100 m backstroke and 200 m backstroke but due to a shoulder injury she did not make the finals. In the 200 meter backstroke event she finished 11th in the semifinals. In the 4 × 100 m medley relay she did swim the final, finishing 6th with the Dutch team. Van Rouwendaal (swimming the backstroke lead-off leg) and her teammates Moniek Nijhuis (breaststroke), Inge Dekker (butterfly), and Ranomi Kromowidjojo (freestyle) broke the Dutch record in this event.