Following an outstanding 2014–15 season, he was selected to play in the 2015 CHL/NHL Top Prospects Game and named to the 2014–15 QMJHL Second All-Star Team.

[15] After competing in the Top Prospects Game, Beauvillier and the Cataractes participated in the QMJHL's inaugural Winter Classic against the Victoriaville Tigres.

[16] He subsequently finished the month as the QMJHL's Second Star of January as he accumulated 25 points through 11 games and excelled in the face-off circle with an efficiency of 57.6%.

[28] His playing success earned him recognition from Team Canada and he was invited to their camp prior to the 2016 World Junior Ice Hockey Championships.

[29] He was eventually named to Team Canada's final roster alongside fellow Islanders prospect Matthew Barzal.

[32] After losing the opening game, Beauvillier recorded five points to lift the Cataractes over the Phoenix to the second round against the Charlottetown Islanders.

[36] Although he set career-highs in the postseason with 30 points, Beauvillier and the Shawinigan Cataractes fell to the Rouyn-Noranda Huskies in Game 5 of the President's Cup Final.

[50] Due to the Islanders lacklustre performance, assistant general manager Doug Weight was named interim head coach midway through the 2016–17 season.

[51] Beauvillier ended the season with nine goals and 15 assists for 24 points through 66 games as the Islanders failed to qualify for the 2017 Stanley Cup playoffs.

[56] Due to his decreased production, Beauvillier was reassigned to the Islanders AHL affiliate, the Bridgeport Sound Tigers, for conditioning.

[62] Due to the departure of John Tavares, new head coach Barry Trotz put Beauvillier on the top line with Barzal and Bailey.

He moved Beauvillier to the top line due to his "natural chemistry with Barzal" and Bailey's high hockey IQ.

He broke his scoreless streak by recording his first career NHL hat-trick on November 15 to help lift the Islanders to a 7–5 win over the New York Rangers.

[68] As the Islanders met with the Pittsburgh Penguins in the Eastern Conference First Round, Beauvillier tallied his first playoff goal during their a 3–1 win in Game 2.

[60] Upon making his season debut, Beauvillier became the second youngest Islander player for the first time in his career as he was nearly 31 months older than Noah Dobson.

[73] As a result of his consistency in scoring, Beauvillier played alongside Brock Nelson and Nick Leddy in high-intensity situations.

[74] However, as injuries plagued the Islanders roster, coach Trotz moved Derick Brassard to the wing alongside Beauvillier and Nelson in late October.

[76] While the Islanders underwent a hot streak, every member of Beauvillier's line produced offensively to maintain their winning record.

[1] Part of his success was due to coach Trotz working individually with Beauvillier to establish a level of trust and responsibility in his designated role.

[80] When the NHL resumed play for the 2020 Stanley Cup playoffs, Beauvillier and the Islanders faced off against the Florida Panthers in the newly created qualifying round.

[92] On May 1, Beauvillier scored two goals in another win over the New York Rangers to help the Islanders clinch a berth in the 2021 Stanley Cup playoffs.

[106] On March 24, Beauvillier set numerous franchise records by scoring a goal within the first nine seconds of their game against the Detroit Red Wings.

His goal was the earliest in any Islander home game, surpassing John Tavares, and second fastest in franchise history behind Bryan Trottier.

[115] On January 30, 2023, Beauvillier was traded to the Vancouver Canucks along with Aatu Räty and a conditional first-round pick in the 2023 NHL Entry Draft for Bo Horvat.

[117] On November 28, 2023, Beauvillier was traded to the Chicago Blackhawks for a conditional fifth-round pick in the 2024 NHL Entry Draft, ending his short stint with Vancouver.

[120] As an unrestricted free agent for the first time in his career, Beauvillier returned to the Metropolitan Division by signing a one-year, $1.25 million contract with the Pittsburgh Penguins on July 1, 2024.

[123] On December 1, 2015, Beauvillier was invited to the Team Canada selection camp for the 2016 World Junior Ice Hockey Championships.

[29] He was eventually named to Team Canada's final roster alongside fellow Islanders prospect Mathew Barzal.

[128] Outside of hockey, Beauvillier helps to raise money and awareness for Alzheimer's after his grandfather was diagnosed and subsequently died from the disease.

[129] In 2018, Beauvillier helped organize the first Spike for Alz charity Spikeball tournament, which raised over $10K worth of donations in its debut.