In the 2001–02 season, Ponsero debuted on the Junior Grand Prix (JGP) series and competed at his first World Junior Championships, finishing 8th. In March 2005, he stepped onto the podium at the World Junior Championships in Kitchener, Ontario, Canada; ranked third in his qualifying group, first in the short program, and second in the free skate, he won the silver medal behind Nobunari Oda of Japan.