Newhook joined the Victoria Grizzlies of the British Columbia Hockey League (BCHL) for the 2017–18 season where he finished second in team scoring with 66 points in 45 games played.
[3] After leading all BCHL skaters in scoring during his final year, he earned the Vern Dye Memorial Award as the league's most valuable player (MVP).
For his efforts, Newhook was named recipient of the Tim Taylor Award, becoming the first such player in Boston College history, as well as the Hockey East Rookie of the Year.
[8] Newhook missed the start of his sophomore season at Boston College due to his participation in the 2021 World Juniors held in Edmonton, Alberta.
Team Canada required their players to quarantine for a full two months ahead of the competition as they held training camp in Red Deer, Alberta.
Continuing into the 2021 Stanley Cup playoffs, he scored his first NHL goal on May 21, 2021, in the third game of the Avalanche's first-round series against the St. Louis Blues.
[14] Newhook made the Avalanche's opening night roster for the 2021–22 season, but coach Jared Bednar sent him back to the Eagles after the first game, seeking "more confidence with the puck."
[17] The Avalanche were unexpectedly upset in the first round of the 2023 Stanley Cup playoffs by the Seattle Kraken, with Newhook registering only one assist in seven games and seeing his ice-time decline.
"[20] As an impending free agent following the conclusion of his entry-level contract with the Avalanche, Newhook was traded to the Montreal Canadiens in exchange for both a first and second round pick in 2023 and prospect Gianni Fairbrother on June 27, 2023.
[27] Enjoying more success in that role, he registered seven goals and six assists, ranking fourth on the team in points, before sustaining a high ankle sprain in a November 30 game against the Florida Panthers which resulted in a prolonged absence.
[34] Newhook was then was named to the national under-18 team for the 2019 IIHF World U18 Championships where he shared Canada’s scoring lead (10 points) along with teammate Peyton Krebs despite their country being unable to secure a podium finish.
[36] He recorded three goals and registered six points at the tournament, helping Canada capture silver after falling to rival United States whom featured fellow Boston College linemate Matthew Boldy as well as Eagles goaltender Spencer Knight.