St-Pierre's debut at an international sporting competition was at the 2010 Commonwealth Games in Dehli, India. He reached the quarterfinals of the men's welterweight competition before losing 13–1 to Carl Hield of the Bahamas. St-Pierre then competed in the 2011 African Games which was held in Maputo, Mozambique. St-Pierre competed in, and won, the men's middleweight competition. He beat Algerian Saad Kaddous in the final. At the 2014 Commonwealth Games in Glasgow, Scotland, St-Pierre competed in the men's light heavyweight competition. He beat David Akankolim of Ghana, Australian Jordan Samardali and Welshman Nathan Thorley to reach the final of the competition. In the final, he lost 3–0 to New Zealander David Nyika and, therefore, claimed the silver medal. He was one of only two Mauritian medalists at the game, with female Judoka Annabelle Laprovidence the other. St-Pierre than competed in the 2015 African Games in Brazzaville, Republic of the Congo. St-Pierre won a gold medal in the men's heavyweight competition, beating Nigerian Efetobor Wesley Apochi in the final.