Viitasuo represented Finland with the national under-18 ice hockey team at the IIHF World Women's U18 Championship in 2012, 2013, and 2014; Finland placed fifth in all three tournaments. Her first match with the women's national team came in August 2014 and her world championship debut was made at the 2016 IIHF Women's World Championship. She played in the women's ice hockey tournament at the 2018 Olympic Winter Games, in which Finland claimed bronze, and at the 2019 IIHF Women's World Championship, in which Finland won their first-ever silver medal.