Born in Gällivare, she is one of the highest-ranking female wrestlers in Europe. She wrestles in the 48 kilo division for the Gällivare SK Wrestling club, coached by Håkan Johansson and Kalle Taivalsaari. Since 2001, she has won eleven Swedish National Championships. In 2007 she competed at the European Championship in Sofia, her first ever international championship at senior level. Despite her young age and inexperience, she won her first match; however, in the following match she was defeated by the Russian wrestler Larisa Oorzhak. In the repechage, Mattsson defeated her other two opponents and won the bronze medal. In August 2007, Mattsson became Junior World Champion for the second time after she defeated the Japanese wrestler Fuyuko Mimura in Beijing. In September the same year, she competed at her first ever World Championship at senior level in Baku, Azerbaijan, where she placed 8th, assuring herself qualification for the 2008 Summer Olympics. In April 2008 the young Swedish wrestler won a silver medal at her second ever European Championship at senior level. That summer, she was defeated in the second round at the Olympics by Clarissa Chun. In September 2009, Mattsson won the Senior World Championship in 51 kg. At the 2012 Summer Olympics, Mattsson competed in the women's lightweight division. She beat Sündeviin Byambatseren in the first round and Marwa Amri in the second, but lost to Valeria Zholobova in the quarterfinals. In 2014, Mattsson competed on the Swedish version of the television showFort Boyard. In June 2015, she competed in the inaugural European Games, for Sweden in wrestling, more specifically, the women's freestyle 55 kg division. She earned a gold medal. On 9 March 2016 Mattsson won the 2016 European Wrestling Championships, she won all wrestling matches by fall. She won the bronze medal in 53 kg at the 2016 Olympic Games in Rio de Janeiro. She did this by beating Odunayo Adekuoroye in the last 16, then Katarzyna Krawczyk in the quarterfinals. She lost to eventual gold medalistHelen Maroulis in the semifinals. Mattsson was entered into the repechage, where she beat Zhong Xuechun to win a bronze medal. She is in the team of Haryana Hammers pro wrestling season2 held in New Delhi.
2006 – 1st at the Junior World Championship in Guatemala
2006 – 1st at the Cadet European Championship in Turkey
2005 – 1st at the Cadet European Championship in Albania
2004 – 1st at the Cadet European Championship in Bulgaria
Trivia
At the European Championship in Sofia, the organisers of the event awarded her with the title "Miss Europe", a prize reserved for the prettiest wrestler at the tournament. However, she refused to accept the prize and commented: "This is not part of the sport. We are here to excel and win at wrestling. There are some people who compete in that other thing too but we don't do that here".
