Vaakanainen represented the Finnish under-18 national team in the 2016 IIHF World U18 Championships with whom he won gold medals and then finished in second place in 2017 IIHF World U18 Championships. He then played for the Finnish under-20 national team in 2017 World Junior Ice Hockey Championships and 2018 World Junior Ice Hockey Championships where they finished ninth and sixth respectively. Vaakanainen would finally win gold in the 2019 World Junior Ice Hockey Championships, his third time in the tournament as Team Finland was victorious against Team USA in the gold medal round.