Reinhart and Aaron Ekblad were the only two players on the Canadian roster eligible for the 2014 NHL Entry Draft. Reinhart registered two goals and three assists in the first three games of the tournament, but was held scoreless for the remainder of the tournament. Canada lost the bronze medal game against Russia 2–1 and finished fourth. Sam Reinhart also represented Team Canada at the 2015 World Junior Ice Hockey Championship. The team won gold as Sam served as one of two alternate captains for the team, the other being Connor McDavid. Reinhart scored the game-winning goal against team Russia in the Gold Medal game, which was his fifth of the tournament. Reinhart finished with a total of 5 goals and 11 points leading all players in goals and points. Reinhart represented Team Canada at the 2016 IIHF World Championship helping win Gold and finishing the tournament with four assists in 10 games. On April 29, 2019, Reinhart was named to the Team Canada roster for the 2019 IIHF World Championship held in Slovakia. Reinhart helped Canada progress through to the playoff rounds before losing the final to Finland to finish with the Silver Medal on May 26, 2019. He finished the tournament posting 3 goals and 5 points in 10 games. In an interview on WGR Sports Radio 550AM, Reinhart stated he prefers to be called "Samson" as opposed to "Sam". Samson's nickname with the Sabres (and 2015 WJC linemate Max Domi) is "Reino." He chose the number 23 as his jersey number for Buffalo, the same number his father Paul Reinhart wore during his NHL tenure.