At the age of six Ann Kristin Flatland moved with her family from Asker to Vik and has since started for the sports club in her hometown Vik . The student was trained by Geir Ole Steinslett . In the biathlon World Cup , she made her debut at the 2003 season opener in Kontiolahti, Finland, finishing 56th in the sprint. At the second World Cup station of the season, she was used in Hochfilzen in the Norwegian relay and was fifth with this. Since then she has been able to occupy several top places with the relay, including a third place in 2006 in Hochfilzen and a second place in 2008 in Ruhpolding .
In 2005 she was used twice at the World Championships in Hochfilzen and finished 22nd in the sprint and 37th in the pursuit. In 2007 she reached fifth place in the sprint at the World Championships in Antholz and won the bronze medal with the relay. In the sprint race in Oberhof in the 2009/2010 season , Ann Kristin Flatland was able to run on the podium for the first time. This third place was her best place in a World Cup individual race to date. Two weeks later she was also third at the World Cup in Antholz, this time in the pursuit. Ann Kristin Flatland took part in the 2010 Olympic Winter Games . Her best result was 8th in the pursuit. In addition, she finished 10th in the sprint, 11th in the mass start and came in 14th in the individual. She finished 4th in the relay. In the 2010/2011 season , she celebrated her first World Cup success in the sprint race in Oberhof.
After the birth of her daughter in April 2012, she started competition training again in the fall. After two first places without shooting errors in front of a home crowd in Beitostølen in the individual race and in the sprint, she was called back to the team for the World Cup in Ruhpolding and won the first race with Hilde Fenne , Synnøve Solemdal and Tora Berger in the relay competition.