Hattestad made her international debut at the 1981 European Junior Championships, finishing fifth. The following year, at the age of just 16, she competed in the European Championships for seniors. By the beginning of the 1990s, Hattestad was one of the best female javelin throwers in the world. In 1993, she won her first major international title, the World Championships in Stuttgart as well as the IAAF Golden Four. To that, she added the 1994 European title. At the 1996 Atlanta Olympic Games, she won the bronze medal. The following year, she regained the World Championships. At the 1999 World Championships, she lost the title again, finishing third, but in 2000 she won the only title missing in her career with a gold medal at the Olympic Games in Sydney.