Lehtonen began her athletic career in
cross-country skiing, competing in national championships in
Finland. Lehtonen made her international debut on 2 March 2017, during the 2016/17
IBU Cup season at a competition held in
Kontiolahti, Finland. She participated in the individual, sprint, and pursuit events, but finished outside the points standings in all three races. At the start of the
2017/18 season, Lehtonen competed in the opening IBU Cup races in
Sjusjøen,
Norway. Following these performances, she was promoted to the Finnish World Cup team. Her first
World Cup race took place in
Hochfilzen,
Austria, in mid-December 2017. In the sprint event, she recorded five shooting misses and finished 95th, missing both the pursuit qualification and points standings. Lehtonen achieved her first World Cup top-10 finish in early January 2018 in
Oberhof, as part of the Finnish women's relay team. Competing alongside
Kaisa Mäkäräinen,
Mari Laukkanen, and
Laura Toivanen, she helped secure a 7th-place finish, marking the best result for a Finnish women’s relay team since the 6th place at the
2003 Biathlon World Championships. Lehtonen made her
Olympic debut at the 2018 Winter Olympics in
Pyeongchang. She competed in the sprint event, finishing 79th, and was part of the Finnish women's relay team that secured 15th place. In December 2024, Lehtonen achieved a career-best performance by finishing 7th in the pursuit event at the Biathlon World Cup in
Annecy,
France. ==Biathlon results==