At the 2016 IIHF World Junior Championships held in Helsinki, Matthews and Matthew Tkachuk each recorded 11 points to lead the United States men's national junior ice hockey team in scoring. After losing in the semifinals, the United States defeated Sweden to win the bronze medal. His seven goals in the tournament were one short of Jeremy Roenick's American record of eight, which was set in 1989. In recognition of his play, Matthews was named to the tournament All-Star Team. Later that year, Matthews played with the United States national men's senior team at the 2016 IIHF World Championship, during which he led the Americans in point scoring.