At the beginning of her sports career, Thompson tried her hand as an alpine ski racer , but she only competed in a few FIS races at the beginning of 2008; best result was a 24th place. She then switched to ski cross. In 2010 she found herself in the national team by winning the overall standings of the Nor-Am Cup and second place at the Canadian championships. She made her debut in the World Cup on December 18, 2010: In Innichen , she finished 21st and immediately won her first World Cup points. The best result in her first season was a 7th place, at the 2011 World Championships in Deer Valley she drove to 15th place. At the end of the season she was Canadian champion.
On December 17, 2011, Thompson achieved her first World Cup podium finish with third place in San Candido, and she celebrated her first World Cup victory on February 3, 2012 in Blue Mountain . With a total of six podium places, including two more victories in Branäs and Grindelwald , she won the Skicross World Cup ranking of the 2011/12 season . At the beginning of the 2012/13 season , Thompson was initially unable to match the performance of the pre-winter season. It was not until February that she achieved another podium finish in Sochi . She won the silver medal at the 2013 World Championships in Voss and the gold medal at the 2013 Junior World Championships in Chiesa in Valmalenco .
In the winter of 2013/14 , Thompson stood on the podium in a World Cup race six times, three times as the winner (in Nakiska , Val Thorens and La Plagne ). She narrowly won the discipline classification in the last race of the season when she was still overtaking Swiss rider Fanny Smith . She won the gold medal at the 2014 Winter Olympics in Sochi, ahead of Kelsey Serwa and Anna Holmlund . In the first half of the 2014-15 season , Thompson continued to be superior. She won in Nakiska and twice in Val Thorens. At the 2015 World Championships on Kreischberg , she was only eighth; she sustained a knee injury during the race and had to end the season early. In the winter of 2015/16 she won four world cup races in Montafon , Watles, as well as in Nakiska and Idre . Together with two second places, this was enough for second place in the discipline ranking.
Thompson dominated the 2016/17 season almost at will. She won seven world cup races in Val Thorens and Arosa , in Montafon and Watles as well as in Idre , Sunny Valley and Blue Mountain . With a large margin, she won the discipline ranking for the third time. On the other hand, at the 2017 World Championships in the Sierra Nevada, she only made fifth place. In the training camp in Saas-Fee , she fell badly and tore a cruciate ligament as well as a ruptured inner ligament. She was fit again in time for the 2018 Winter Olympics in Pyeongchang . There she set the fastest time in qualifying, but was eliminated in the first round.