[citation needed] On August 19, 2019, Dean signed with the Gatineau Olympiques of the Quebec Major Junior Hockey League (QMJHL).
Dean was selected by the Vegas Golden Knights with the 30th overall pick in the 2021 NHL Entry Draft, and signed a three-year, entry-level contract on December 2, 2021.
[2] While playing with the Olympiques in the 2022–23 season, Dean was traded by the Golden Knights to the St. Louis Blues in exchange for Ivan Barbashev on February 26, 2023.
[4] Dean appeared for the Canada Black team at the 2019 World U-17 Hockey Challenge, recording five points in seven games.
On December 12, 2022, Dean was named to Team Canada to compete at the 2023 World Junior Ice Hockey Championships.