Holmström represented Sweden at the 2013 Ivan Hlinka Memorial Tournament, where he recorded one assist in four games. He later represented Sweden at the 2014 IIHF World U18 Championships, where he was second-leading scorer during the tournament, recording three goals and eight assists in seven games. Holmström represented Sweden at the 2015 World Junior Ice Hockey Championships, where he recorded one goal and six assists in seven games. Holmström again represented Sweden at the 2016 World Junior Ice Hockey Championships, where he recorded one goal and five assists in seven games.