Joubert took part in few international events as a junior. His first major international competition was the 2000 World Junior Championships, where he placed 15th. The following season, he placed 4th at both his junior Grand Prix assignments, and later finished 14th at senior nationals, and failed to qualify for the French team for 2001 Junior Worlds. The president of the French Ice Sports Federation, Didier Gailhaguet, entered Joubert in the 2001 Top Jump competition, where he placed second. Joubert turned senior following the 2000–2001 season.