The younger brother of the world and Olympic champion Petter Northug won the gold medal in the sprint competition and with the Norwegian relay at the Nordic Junior World Championships 2010 in Hinterzarten . A year earlier he had already impressed at the 2009 Junior World Championships in Praz de Lys Sommand, where he won the bronze medal with the Norwegian relay and was able to achieve top ten placements in the individual competitions. After an eighth place in the Scandinavian Cup in Lygna , he was nominated in March 2010 for his first World Cup race . At the Sprint World Cup in Drammen , he survived the qualification and, as 30th, won a World Cup point at his first World Cup start. After he was able to convince in sprint competitions of the Scandinavian Cup in the 2010/11 season , he was nominated for the World Cup in Liberec , where he achieved his best career result with 18th place. At home in Drammen, he was able to improve this result and achieved 14th place. At the beginning of the 2011/12 season, he made it to a semi-finals for the first time in Düsseldorf , but where he was eliminated and took twelfth place. In the 2012/13 and 2013/14 seasons he mainly started in the Scandinavian Cup, in which he won three races and in 2013 the overall standings. At the beginning of the 2014/15 season he achieved his first top ten placement in the World Cup with eighth place in the sprint in Ruka . This was followed by a sixth place in the sprint in Davos . In January 2015 he won his first World Cup victory in the sprint in Otepää . He finished sixth at the 2015 Nordic World Ski Championships in Falun . He finished the season in seventh place in the Sprint World Cup.