Stjernen made his international debut on February 12, 2005 at the Continental Cup jumping competition in Brotterode . In the two competitions he reached 49th place. At the Junior World Championships in 2005 in Finnish Rovaniemi he reached the sixth place with the team. From September 2005 to January 2006 Stjernen competed in the FIS Cup . At the Junior World Championships in 2006 in Kranj , he was nineteenth in the individual and fifth in the team competition. From March 2006 he started again in the Continental Cup. He was able to win Continental Cup points for the first time on March 12, 2006 in Bischofshofen . At the Junior World Championships 2007 in Tarvisio he jumped again with the team to fifth place. In the individual he came in 44th place. After increasing his performance, he started the qualification for the World Cup ski flying in Vikersund on March 15, 2009 . He could not qualify for jumping with 49th place. On December 5, 2009, he started for the first time in a World Cup competition in Lillehammer and with a 19th place also won World Cup points for the first time. He achieved his first top ten placement in the World Cup on January 15, 2011 in Sapporo with eighth place. On March 5, 2011, Stjernen won a competition in the Continental Cup for the first time in Kuopio . In the following winter of 2011/12 he dominated the Continental Cup with five wins and two further podium finishes, so that in the end he was able to secure the overall standings.
On February 16, 2013 Stjernen achieved his first World Cup podium with a second place in ski flying on the Heini-Klopfer ski flying hill in Oberstdorf . A day later, he won the team ski flying with the Norwegian team as part of the FIS Team Tour 2013 and not only achieved his first World Cup victory, but also contributed to the overall victory of the Norwegians in the team tour, which was the previous leading due to the day's victory Slovenian selection could still intercept. At the Nordic World Ski Championships in 2013 in Val di Fiemme , he finished 13th in the individual on the normal hill and 18th on the large hill. He finished fourth with the team. At the end of the 2012/13 season, Stjernen took third place in the overall ski flying ranking.
On August 15, 2014, he won a competition in the Summer Grand Prix for the first time while jumping in Courchevel, France .
In the 2015/16 World Cup season , Stjernen was able to achieve his second and third podium places in an individual competition. He came third both in December 2015 on the normal hill in Lillehammer and in February 2016 on the flying hill in Vikersund. With twelfth place in the overall World Cup, he achieved his best result to date. At the Nordic World Ski Championships in Lahti in 2017 , he finished 17th in the individual competition on the normal hill and fifth in the mixed team competition with the Norwegian team. In the individual competition on the large hill, he just missed a medal as fourth. In the team competition he won the silver medal behind world champion Poland together with Anders Fannemel , Johann André Forfang and Daniel-André Tande . On March 16, 2017, he achieved another podium finish in second place in Trondheim . In the overall World Cup 2016/17 , he finished twelfth, repeating the result from the previous season.
Gold medal in the team competition of the 2018 Olympic Winter Games
On January 13, 2018, he was able to win an individual competition in the World Cup for the first time in ski flying in Bad Mitterndorf . At the Ski Flying World Championships 2018 in Oberstdorf , he finished fifth in the individual. In the team competition, he was able to win the gold medal together with Robert Johansson , Johann André Forfang and Daniel-André Tande. At the 2018 Winter Olympics in Pyeongchang , South Korea , he took 15th place in the individual competition on the normal hill and eighth place in the individual competition on the large hill . In the team competition on the large hill , he and Daniel-André Tande, Johann André Forfang and Robert Johansson won the gold medal in front of the teams from Germany and Poland. After his victory in ski flying on the Kulm, he took second place in Vikersund in ski flying competitions at the end of the season as well as eighth and fifth places in Planica . With these results, he won the ski flying competition 2017/18.
At the national competition on the Granåsen large hill in Trondheim , Stjernen became Norwegian champion on January 15, 2019. At the 2019 World Championships in Seefeld in Tirol , Austria , he won the bronze medal in the final mixed team competition together with Anna Odine Strøm , Maren Lundby and Robert Johansson . Before that, he had reached 29th place on the large hill and 25th place on the normal hill in the individual competitions and had finished fifth with the Norwegian team in the men's team competition. After he and Thomas Aasen Markeng ranked seventh after the first round of the normal hill competition at Toni-Seelos-Olympiaschanze , he fell back to 25th place in increasingly difficult conditions in the second round. The sporting director of the German team, Horst Hüttel, criticized the jury for not intervening because of the heavy snowfall: “The second round was completely irregular. If that is not irregular, then I no longer understand the world. There is competition management for this. They failed miserably. ”The Austrian association president Peter Schröcksnadel also spoke of a lottery and criticized sticking to the schedule:
"We were lucky. We won a bronze in the lottery and we're happy about that. It was a crazy jump and not regular for me. (…) If you had to wait a little longer you could have covered the heaviest snowfall, the quick pulling through just for television was not right. "
At the beginning of March 2019, the then 30-year-old Stjernen announced the end of his career after Raw Air 2019 . After all, he ended his career during Raw Air after jumping in Trondheim on March 14, 2019. In his last jump he reached a podium again with second place behind Ryoyu Kobayashi .
Personal
Andreas Stjernen is the son of the former ski jumper and functionary Hroar Stjernen (* 1961).