Amânar began participating in gymnastics as a 6-year-old, and became a national team member in 1994, winning the World and European team titles that year. The following year, she was again part of the winning Romanian team at the World Championships, while winning an individual gold medal in the horse vault, her strongest event.
At the 1996 Summer Olympics, Amânar would win that same event. In the all-around competition, she hadn't placed for the final, but was favoured instead of a teammate and eventually ended up sharing the bronze medal. She won two more medals, a silver in the floor exercise and a bronze in the team all-around.
Amanar continued to be a top performer in the horse vault, winning the world title again in 1997, and team titles in 1997 and 1999.
At the 2000 Summer Olympics, the top favourite for the all-around title, Svetlana Khorkina of Russia, stumbled in a number of events, leaving the title up for grabs for the three Romanian women competing in the final. Andreea Răducan finished first, trailed by Amânar and Simona Olaru. However, it was later discovered that Răducan had used a cold medicine containing banned substances. Although she was not banned, and her results in other events were allowed to stand, Răducan was stripped of her gold medal, which now went to Amânar instead. Earlier in the Olympics, the Romanian women had already secured the team title. In the floor exercise, she won her seventh Olympic medal, a bronze one.