Junior McLeod played
minor ice hockey with the Toronto Marlboros of the
Greater Toronto Hockey League. In 2014, he led his team to capture the
OHL Cup and was awarded the
Tim Adams Memorial Trophy as OHL Cup's most valuable player. McLeod was drafted by the
Mississauga Steelheads of the
Ontario Hockey League (OHL) in the first round (fifth overall) of the 2014 OHL Priority Selection, and played for them beginning with the
2014–15 OHL season. McLeod was named an
alternate captain during the
2015–16 OHL season and named the fifth
captain of the Steelheads in the following
2016–17 season. During the 2016–17 season, McLeod was named OHL Player of the Week on February 27, 2017, after registering five goals and 11 points in three games.
Professional McLeod was selected with the 12th overall pick by the
New Jersey Devils of the
National Hockey League (NHL) in the
2016 NHL entry draft. On October 7, 2016, the Devils signed McLeod to a three-year, entry-level contract. In a preseason game on September 25, 2017, McLeod
tore his meniscus in his left knee and required
arthroscopic surgery. When he was activated from injured reserve he was reassigned to the Mississauga Steelheads. On April 3, 2018, McLeod was assigned to the
Binghamton Devils of the
American Hockey League (AHL) following the conclusion of his OHL career. McLeod was recalled for the first time by New Jersey on November 29, 2018, following
Jean-Sébastien Dea being picked up on
waivers by the
Pittsburgh Penguins. He made his NHL debut the following night in a 6–3 loss to the
Washington Capitals, and was sent back to Binghamton the following day. McLeod got into 21 games with the Devils during the
2018–19 season, registering just three points (all assists). On January 27, 2021, McLeod scored his first NHL goal in a 5–3 loss to the
Philadelphia Flyers, his 39th game. McLeod set a career high in points in a season during the
2022–23 season, registering 26 points in 80 games. On May 1, 2023, McLeod scored the first and ultimately game- and series-winning goal in New Jersey's 4–0 win over the rival
New York Rangers in game 7 of the first round of the
2023 Stanley Cup playoffs. He finished the playoffs with two goals and six points in 12 playoff games for the Devils. On January 24, 2024, the Devils announced that McLeod and defenceman
Cal Foote were granted indefinite leaves of absence from the team. At the end of the season, in which he did not return to play, he had 19 points in 45 games on the strength of a career-best 10 goals. On August 2, 2024, McLeod signed a one-year contract with
Barys Astana of the
Kontinental Hockey League (KHL), joining former Devils teammate
Will Butcher with the Kazakhstani club to start the
2024–25 season. On September 11, 2025, the NHL announced McLeod would be eligible to sign a contract on October 15, and would be eligible to return to play on December 1. ==International play==