Playing his first full season in 2019–20, he made an immediate impact and won the Calder Memorial Trophy as rookie of the year. In his second professional season he was nominated for the James Norris Memorial Trophy, awarded to the league's best defenceman, and won the Norris in the following 2022; he later won a second Norris in the 2025, in his fifth nomination. Makar won the Stanley Cup with the Avalanche in 2022, winning the Conn Smythe Trophy as the most valuable player in the 2022 playoffs. He has been widely cited as one of the best defencemen and best players in the modern NHL.
Internationally, Makar has played for the Canadian junior team, winning gold at the 2018 World Junior Championships. With the senior national team, he won gold at the 2025 4 Nations Face-Off and silver at the 2026 Winter Olympics.