The San Jose Sharks added another core piece to their future when they chose Celebrini with the No. 1 pick in the 2024 NHL Draft and signed the forward to an entry-level contract July 6, 2024. He had a goal and an assist in his NHL debut, a 5-4 overtime loss to the St. Louis Blues at SAP Center on Oct. 10. His goal at 7:01 of the first period was the second-fastest in NHL history by a player selected with the No. 1 pick behind Mario Lemieux, who scored his first goal for the Pittsburgh Penguins 2:59 into his debut Oct. 11, 1984.

Celebrini scored his first NHL hat trick and had two assists in an 8-7 loss to the Minnesota Wild on April 9, 2025, to become the sixth 18-year-old in NHL history with a five-point game, joining Connor Bedard (March 12, 2024), Ryan Nugent-Hopkins (Nov. 19, 2011), Ilya Kovalchuk (Jan. 19, 2002), Dale Hawerchuk (March 13, 1982) and Jack Hamilton (Dec. 4, 1943). He was also the first Sharks rookie and seventh different player with at least five points in one game.

Though Celebrini's rookie NHL season was delayed by missing 12 games with an injury, he did not miss a beat after returning. He was named the NHL Rookie of the Month for November after leading first-year players in goals (seven), points (12) and shots on goal (45), and the NHL First Star for the week ending Dec. 1, 2024, when he had seven points (four goals, three assists) in four games.

He scored twice in the third period and had an assist for his first three-point game in the NHL when the Sharks defeated the Los Angeles Kings 7-2 at SAP Center on Nov. 25. At 18 years and 165 days, Celebrini became the youngest player in Sharks history with a three-point game, besting Patrick Marleau's previous record of 18 years and 171 days when he had three points (one goal, two assists) against the Detroit Red Wings on March 5, 1998. The accolades made Celebrini a finalist for the Calder Trophy given to the NHL rookie of the year.

Celebrini was named to Team Canada's roster for the Olympic Winter Games Milano Cortina 2026, where his goal in the second period of a 10-2 win against Team France on Feb. 15 made him the first NHL player to score on a penalty shot at the Olympics and third in a tournament with NHL participation (Evgeny Koreshkov, Team Kazakhstan on Feb. 21, 2006; Andrejs Maticins, Team Latvia, Feb. 14, 2002). He was also the third from Canada to take a penalty shot and first to score at an Olympics with NHL players following Corey Perry (Feb. 14, 2014) and Sidney Crosby (Feb. 23, 2010).

He won a silver medal and finished with 10 points (five points, five assists), second in the tournament behind Connor McDavid's 13 and the most by a teenager in an Olympics featuring NHL players. He also led the Olympics in goals, which tied Jarome Iginla from 2010 in Vancouver for the most by a Canadian in a single Games with NHL participation.

Celebrini became the first teenager in Sharks history to score 30 goals in a season while adding three assists in a 7-5 win against the Montreal Canadiens on March 3, 2026. His fifth game with at least four points passed Jimmy Carson (four) for the fourth-most by a teenager in NHL history, behind Wayne Gretzky (14), Crosby (eight) and Hawerchuk (seven).

His two goals and two assists in San Jose's 4-3 win against the Anaheim Ducks on April 1 made him the fifth Sharks skater to score at least 40 goals since the franchise joined the NHL for the 1991-92 season (Jonathan Cheechoo, 56 in 2005-06; Owen Nolan, 44 in 1999-00; Marleau, 44 in 2009-10; Joe Pavelski, 41 in 2013-14). His 102nd point passed Erik Karlsson (101; 2022-23) for the second-most in a season in Sharks history behind Joe Thornton (114; 2006-07), and his 115 points (45 goals, 70 assists) in 82 games set a Sharks single-season record.

Celebrini had 64 points (32 goals, 32 assists) in 38 games as a freshman, and at 17 became the youngest player to win the Hobey Baker Award as the top men's player in NCAA ice hockey and fourth from Boston University, joining Jack Eichel (2015), Matt Gilroy (2009) and Chris Drury (1998). He was named rookie of the year and player of the year in Hockey East, joining Eichel (2015), Paul Kariya (1993) and Brian Leetch (1987) as those to win both awards in the same season.

The North Vancouver, British Columbia, native was the fourth player from NCAA men's college hockey chosen No. 1 in the NHL Draft, and first since University of Michigan defenseman Owen Power by the Buffalo Sabres in 2021. He decided to advance his development playing Tier 1 AAA hockey for the San Jose Junior Sharks, prep school hockey at Shattuck-St. Mary's in Minnesota and with Chicago of the United States Hockey League before joining Boston University.

Celebrini was the second player in the history of the USHL to win Player of the Year, Rookie of the Year and Forward of the Year in the same season after leading the league with 46 goals and 86 points in 50 games for Chicago in 2022-23.