Junior Fleury was drafted in the fourth round, 78th overall, by the
Kootenay Ice of the
Western Hockey League (WHL) in the 2013
WHL bantam draft. Fleury played his first campaign with the Ice during the
2014–15 season, putting up one
goal and 13
points through 70 games. On January 12, 2016, He was named
alternate captain of the Ice. During the
2015–16 season, he tallied eight goals and 17
assists in 61 games. On January 17, 2017, Fleury was named
captain of the Ice, in part due to the trade of alternate captains Zak Zborosky and Matt Alfaro the week before. On January 28, he was named to Team Cherry for the 2017
CHL/NHL Top Prospects Game after an injury was sustained to
Seattle Thunderbirds defenceman Jarret Tyszka. Team Cherry won the game 7–5 over Team Orr, and Fleury recorded three shots but no points. Fleury finished the 2016–17 season with 11 goals and 27 assists through 70 games. His work caused him to be ranked 62nd overall among North American skaters in the final NHL Bureau of Central Scouting ranking. Fleury was selected 87th overall by the
Montreal Canadiens in the
2017 NHL entry draft on July 24, 2017. On November 11, he was traded to the
Regina Pats in exchange for defenceman Jonathan Smart and forward Cole Muir, as well as other WHL bantam draft picks. In 17 games before being traded, Fleury had achieved six goals and four assists. With the Pats, he notched six goals and 35 assists through 51 games. In seven playoff games, he tallied four assists. He helped the Pats reach the
2018 Memorial Cup, where he managed one assist. However, the Pats lost the Memorial Cup Final 3–0 to the Acadie Bathurst Titan.
Professional Montreal Canadiens Fleury was a participant in the Canadiens' 2018 training camp, and on October 4, 2018, he signed a three-year
entry-level contract with the team. Fleury played 60 games with the Rocket during the
2018–19 season, ending with nine goals and 14 assists. On October 1, 2019, it was announced that Fleury would appear in the Canadiens' opening night roster for the
2019–20 season. He made his NHL debut on October 3 against the
Carolina Hurricanes, for whom his brother
Haydn played at the time. On November 16, 2019, he scored his first NHL goal during a 4–3 overtime loss to the
New Jersey Devils. On January 21, 2020, Fleury was assigned to the Rocket. His one goal was the only point he collected through 41 games that season with the Canadiens. Through 14 games with the Rocket, he put up two goals and three assists. To start the
2020–21 season, Fleury was named to the Canadiens'
taxi squad, taxi squads being a safety measure put in place by the NHL for that season due to the
COVID-19 pandemic. However, Fleury spent much of his time during the season with Laval, totaling six assists in 22 games.
Seattle Kraken On July 18, 2021, the protected player lists for the
2021 NHL expansion draft were released, which did not include Fleury. On July 21, he was selected from the Canadiens at the draft by the
Seattle Kraken, reuniting him with his brother Haydn. On August 13, the Kraken signed him to a one-year, entry-level contract. Fleury was sent down to the Kraken's AHL affiliate, the
Charlotte Checkers, of whom he was named an assistant captain. On January 24, 2022, after playing 36 games with Charlotte, he was recalled to the Kraken's taxi squad. He made his Kraken debut on February 1 against the Boston Bruins, playing on the same defensive pairing as his brother. Fleury was sent back down to the Checkers on February 3 after totaling two games with the Kraken. He was once again recalled by the Kraken on April 5, after collecting seven goals and 26 assists in 58 games with the Checkers. On April 28, after playing seven more games with the Kraken, he was returned to the Checkers. During the
2022 Calder Cup playoffs with the Checkers, Fleury notched three assists. During the
2022–23 season, Fleury played in 12 games with the Kraken, registering one assist. On July 9, 2023, He signed a two-year, contract with the Kraken. For the
2023–24 season, he was named to the opening roster of the
Coachella Valley Firebirds, the Kraken's new AHL affiliate. Through 65 games with the Firebirds that season, Fleury tallied seven goals and 29 assists. He played one game with the Kraken that season on April 5, 2024, taking the place of
Adam Larsson and registering 13:30 of ice time. During the Firebirds' run during the 2024 Calder Cup playoffs, which took them to the Calder Cup Final, Fleury registered five goals and nine assists in 18 games. On October 18, 2024, Fleury recorded his first professional
hat-trick as part of a 6–5 victory over the
San Diego Gulls. On January 8, 2025, he was named to participate in the 2025
AHL All-Star Classic. However, on January 30, he was called up by the Kraken. This made him unable to participate in the All-Star Classic, and his roster spot was given to teammate
Jani Nyman. Fleury ended the 2024–25 season with the Firebirds earning seven goals and 19 assists in 39 games. Through 14 games with the Kraken that season, he had only one assist. On June 20, Fleury signed a two-year contract extension with the Kraken, worth per year. ==Personal life==