In 2006, García Belmonte Junior World champion in the 400 m freestyle and the 400 m medley. Furthermore, she was European Junior Champion over the same distances.
2008 was the most successful year in the young career of Mireia Belmonte García. At first she was later with a new European Championship record in the 200 m medley European champion at the European Swimming Championships 2008 in Eindhoven and then, less than three weeks, at the Short Course World Championships 2008 in Manchester, she was with a new European record vice-world champion in the 200m individual medley.
At the 2012 Summer Olympic Games in London, Belmonte swam the 200m butterfly and the 800m freestyle one silver medal.