Born and raised in Long Beach, New York, McAvoy started skating at the age of 3 at Long Beach Arena, where his father, Charlie Sr., helped install a studio rink as a plumbing and heating contractor.
McAvoy grew up a fan of the New York Rangers and Hockey Hall of Fame defenseman Brian Leetch, and attended Long Beach High School for one year before moving to Ann Arbor, Michigan, to join USA Hockey’s National Team Development Program.
McAvoy played two seasons with the NTDP and helped the United States win the gold medal at the 2015 IIHF Under-18 World Championship before heading back east to play at Boston University as a 17-year-old freshman.
Following his freshman season, during which he led the team’s defensemen with 25 points (three goals, 22 assists) in 37 games, McAvoy was selected by the Boston Bruins with the No. 14 pick in the 2016 NHL Draft.
McAvoy was named a CCM/ACHA First Team All-American as a sophomore, when he had 26 points (five goals, 21 assists) in 38 games. He also won a gold medal for the United States at the 2017 IIHF World Junior Championship.
After signing a three-year, entry-level contract with the Bruins on April 10, 2017, McAvoy made his NHL debut in Game 1 of the Eastern Conference First Round against the Ottawa Senators. He played in all six games of the series, getting three assists while averaging 26:12 of ice time per game.
The following season, McAvoy was named to the NHL All-Rookie Team after he had 32 points (seven goals, 25 assists) and a plus-20 rating in 63 games.