[2] During the 2019–20 season, on January 1, 2020, after losing several forwards to injury, the Maple Leafs called up Marchment to make his NHL debut the following night against the Winnipeg Jets.

[3][4] He registered one assist in four appearances with the Maple Leafs, across multiple callups before he was traded by Toronto to the Florida Panthers in exchange for Denis Malgin on February 19, 2020.

[8] On February 18, 2022, Marchment scored his first career hat trick in a 6–2 Florida Panthers win over the Minnesota Wild.

[9] As a free agent from the Panthers, Marchment was signed to a four-year, $18 million contract with the Dallas Stars on July 13, 2022.

[10] In his first game with the Stars, Marchment recorded 2 goals to lead his team to a win over the Nashville Predators.