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 (featherwight) 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 medalist Helen Maroulis in the semifinals. Mattsson was entered into the repechage, where she beat Zhong Xuechun to win a bronze medal.