Weir won the Junior Eastern Sectionals in 1999 and 2000. The following season (2000–2001), Weir competed as a senior for the first time, coming in sixth place at the U.S. Nationals despite "a bad hip flexor injury", and winning the Eastern Sectionals as a senior. He was the third alternate at the 2000 Junior Grand Prix final, coming in sixth and second place at his two Junior Grand Prix assignments, but won, at the age of 16, the gold medal at the World Junior Championships. He was the tenth American to win at Junior Worlds and the first American male skater since Derrick Delmore won in 1998. Lysacek won the silver medal; it was the first time since Rudy Galindo and Todd Eldredge in 1987 that American men came in first and second place. Despite falling on the simplest jump in his short program, a triple flip, Weir was placed first going into the free skate. Weir received the best artistic scores, receiving 5.7s for presentation in his free skate.