Moceanu trained under Marta and Béla Károlyi, and later Luminița Miscenco and Mary Lee Tracy. She earned her first national team berth at age 10 and represented the United States in various international competitions at the junior level. She was the all-around silver medalist at the 1992 Junior Pan American Games and the 1994 junior national champion. In 1995, at the age of 13, she became the youngest gymnast to win the senior all-around title at the U.S. National Championships. She was the youngest member of both the 1995 World Championships team and the gold-medal-winning 1996 Olympics team, and was the last gymnast to compete legally in the Olympics at the age of 14.