Yannick Letailleur made his debut in Langdorf in 2004 in the Junior European Cup. In 2005 he took part in his first Junior World Championship in Kontiolahti and achieved his best result in the sprint as 23rd. In the following year, the result in the sprint with 29th place in Presque Isle was the best result. The 2007 World Cup in Martell was particularly successful . In the sprint, Letailleur was only 65th, but in the individual he was 13th and in the relay he won the bronze medal with Marc-André Bédard , Maxime Leboeuf and Brendan Green .