[3] Contextually, Matheson cited personal motivation for leaving his native Quebec as the ability to develop better as a player in both the USHL and in the NCAA.

[7] Amid rumours of him leaving the college ranks to sign with NHL draft team, the Florida Panthers, Matheson decided to remain as part of the Eagles for the 2014–15 season.

[11] Initially assigned to the Panthers' newfound AHL affiliate the Portland Pirates[12] to begin the 2015–16 season,[13] Matheson made his NHL debut in a 3–1 win over the Winnipeg Jets on February 20, 2016.

[14] Similarly, he made his Stanley Cup playoffs debut for Game 2 of the Panthers' first round matchup with the New York Islanders on April 15.

[29] Despite missing significant playing time over the course of the campaign, Matheson received recognition as the team's annual recipient of the Jean Béliveau Trophy, awarded to the player who exemplifies leadership qualities within the community.

[30] In advance of the 2023–24 season, with the departure of fellow blueliner Joel Edmundson to the Washington Capitals, Matheson was named as an alternate captain of the Canadiens organization.

[34] Internationally, Matheson first represented Canada as part of the national U18 team at the 2011 Ivan Hlinka Memorial Cup, winning a gold medal.

[44] In 2012, Matheson met Emily Pfalzer, an American professional ice hockey player and Olympic gold medalist, while both were playing at Boston College.