[2] Thereafter, he joined the Lincoln Stars of the United States Hockey League (USHL) for a single season where he was named to the USHL/NHL Top Prospects Game in January 2017, recording a shutout for the first time in the history of the showcase.

[6] The following season, he pushed the Huskies even further, winning a record 25 games for the program[5] and earned Tournament MVP honors whereas Northeastern won their third Hockey East distinction.

[12] Playing primarily for Laval over the course of the 2021–22 and 2022–23 campaigns,[13] the Canadiens began the 2023–24 season with three goaltenders on their active roster: Jake Allen, Sam Montembeault, and Primeau, with the latter no longer exempt from waivers and thus unable to be reassigned to the AHL ranks without the possibility of being lost to another team.

[14] After months of a continuous rotation system, Allen was ultimately dealt to the New Jersey Devils on March 8, 2024,[15] allowing Primeau to assume the role as the Canadiens' primary back-up goaltender.

[29] He then participated in the annual World Junior A Challenge where he went 3-1 en route to a gold medal victory, and was subsequently named to the tournament's All-Star Team.

[35] He is the son of former NHL centerman Keith Primeau, and was born in Farmington Hills, Michigan prior to the family moving to Voorhees, New Jersey when Cayden was five months old following his father's trade to the Philadelphia Flyers, in January 2000.