After winning a total of eight medals (including six gold medals) at junior world championships, Tschepalowa took part in world cup races for the first time in the 1995/96 season. She celebrated her first major success at the 1998 Winter Olympics by winning the gold medal in the 30 km run. This made her the youngest ever Olympic cross-country champion. Two more medals were added at the 2001 World Cup, including the gold one with the relay. In the same year she became the overall winner of the cross-country skiing world cup .
At the 2002 Winter Olympics , Tschepalowa secured a complete set of medals (gold in the sprint, silver over 10 km, bronze over 15 km). After a baby break (her daughter Olesja was born on January 10, 2003), she continued her career and was awarded the Holmenkollen Medal in 2004. In 2005 she won four medals at the World Championships, including a gold medal in the 15 km pursuit. At the 2006 Winter Olympics , she won gold in the relay and silver in the 30 km race. In the 2006/07 season she took another break from competition due to pregnancy, and in February she gave birth to daughter Vasilina. In the 2007/08 season she returned to the Cross-Country World Cup, but could not place in the front field. On the last stage of the Tour de Ski 2008/09 , the mountain pursuit in Val di Fiemme , she convinced again for the first time with a tenth place, so that she was able to work her way up from 31st place to 23rd place. At the Nordic World Ski Championships in Liberec in 2009 , her best result was 20th place over 30 kilometers freestyle (mass start).
In August 2009 it became known that Chepalova had tested positive for the doping agent erythropoietin (EPO) on January 3, 2009 on the penultimate stage of the Tour de Ski in Val di Fiemme , whereupon she announced her retirement from competitive sports with immediate effect. In December 2009, Tschepalowa was banned for doping retroactively from August 2009 for two years. The Russian Ski Association then announced that it would appeal this decision to the International Court of Justice for Sports . Tschepalowa himself denies the use of doping substances. Her father and trainer Anatoly Tschepalow explained that his daughter had had thyroid problems for a long time and was therefore banned from starting after a medical examination in August.