 Pari gbolohun ti o tẹle: Ni Oṣu Kẹrin Ọjọ 29, Ọdun 2019, Marchessault ni a yan si idije kariaye akọkọ rẹ lẹhin ti a darukọ rẹ si ẹgbẹ ẹgbẹ Canada fun : 2019 IIHF World Championship, tí ó wáyé ní Slovakia. O wa ni ila akọkọ ti Ilu Kanada o ṣe iranlọwọ fun Ilu Kanada lati ni ilọsiwaju nipasẹ awọn iyipo ere idaraya ṣaaju ki o to padanu ikẹhin si Finland lati pari pẹlu Ogun fadaka ni Oṣu Karun ọjọ 26, ọdun 2019. Marchessault pari idije naa pẹlu awọn ibi-afẹde 3 ati awọn aaye 10 ni awọn ere 10. 