In November 1991, Monnier placed 16th at the 1992 World Junior Championships in Hull, Quebec. The following season, making his senior international debut, he placed 13th at the Grand Prix International St. Gervais. He competed on both senior and junior levels for several years, winning the silver medal at the 1994 International St. Gervais (senior), gold at the 1994 Blue Swords (junior), bronze at the 1995 Ondrej Nepela Memorial (senior), and silver at the 1995 Blue Swords (junior). His final junior appearance came in November–December 1995 at the 1996 World Junior Championships in Brisbane, Australia; he placed 6th in his qualifying group, 11th in the short program, 17th in the free skate, and 14th overall.