After one of the greatest under-20 seasons in Swedish Hockey League (SHL) history in 2017–18, and winning the Le Mat Trophy with the Växjö Lakers, Pettersson made the Canucks' opening night roster for the 2018–19 season. He won the Calder Memorial Trophy as the league's best rookie in 2018–19, becoming the second Canuck to do so after Pavel Bure in 1991–92.