Holund was Junior World Champion over 10 km in the classic technique in Mals in 2008, and one year later he won bronze in both ski and relay competitions at the Junior World Championships in Praz de Lys Sommand . On March 8, 2009 he made his debut in the World Cup in Lahti over 15 km freestyle , which he finished in 52nd place. In the 2012/13 season he took third place in the overall ranking of the Scandinavian Cup. He achieved three podium finishes including two wins. He achieved his first World Cup points in March 2013 at the 50 km freestyle mass start race in Oslo , where he finished 16th. At the World Cup in Rybinsk in January 2015, he reached 11th place in both the 15 km freestyle and two days later in the skiathlon, making it the top 15 in World Cup races for the first time. On February 15, 2015 he finished the 15 km freestyle race in Östersund in fourth place. In the Scandinavian Cup he came third twice and second once. In Madona he took his third victory in the Scandinavian Cup over 15 km freestyle and won the overall standings at the end of the season. After finishing ninth at the Nordic Opening in Ruka at the beginning of the 2015/16 season, he achieved his first podium finish in the World Cup with third place in the skiathlon in Lillehammer and his first World Cup victory the day after with the relay. He finished the 2016 Tour de Ski in 15th place. In January 2016 he became the Norwegian relay champion. The following month he came on the podium again at the World Cup in Lahti with third place in the skiathlon. At the end of the season he achieved eighth place in the Ski Tour Canada and reached tenth place in the overall World Cup and seventh place in the Distance World Cup. At the beginning of the 2016/17 season he came 14th in the World Cup mini tour in Lillehammer. In the Tour de Ski 2016/17 he finished ninth and ran at the final stage of the third fastest time. In February 2017 he took third place over 15 km classic at the World Cup in Otepää and was again Norwegian champion with the relay in Lygna . At the season highlight of the Nordic World Ski Championships 2017 in Lahti, he achieved tenth place in the 50 km mass start race. At the end of the season he came in 15th place at the World Cup final in Québec and reached 12th place in the overall World Cup and tenth place in the Distance World Cup.
In the 2017/18 season, Holund took ninth place in the Ruka Triple and fifth place in the Tour de Ski 2017/18 . In the final stage of the Ruka Triple, he ran the third fastest time and took third place in the skiathlon at the World Cup in Lillehammer . At the season highlight, the 2018 Winter Olympics in Pyeongchang , he won the bronze medal in the skiathlon. He was also there over 15 km freestyle and sixth in the 50 km mass start race. At the end of the season he finished sixth at the World Cup finals in Falun . He achieved second place in the final stage and finally reached sixth place in the overall World Cup and third place in the Distance World Cup. In the following season he finished 13th in the Lillehammer Triple, 12th in the Tour de Ski 2018/19 and 14th in the World Cup finals in Québec, reaching 17th place in the overall World Cup and 12th place 3rd place in the Distance World Cup. He was also third in the relay in Beitostølen and Ulricehamn . At the beginning of February 2019 he became Norwegian champion with the relay and third over 15 km classic in Meråker . At the Nordic World Ski Championships 2019 in Seefeld in Tirol , he won the gold medal in the 50 km mass start race.
At the beginning of the 2019/20 season, Holund won the pursuit race at the Ruka Triple, which he finished in sixth place and in Lillehammer took second place in the skiathlon and third place in the relay. At the 2020 ski tour, he finished third in the pursuit in Trondheim , third. At the end of the season he triumphed in Lahti with the relay and achieved third place over 15 km classic and finally reached seventh place in the overall World Cup and fifth place in the Distance World Cup.