Chabot, a defenseman taken by the Ottawa Senators in the first round (No. 18) of the 2015 NHL Draft, had a solid rookie season in 2017-18, finishing with 25 points (nine goals, 16 assists) in 63 games.

Chabot had his breakout season in 2018-19, finishing with 55 points (14 goals, 41 assists) in 70 games, ranking him 10th among NHL defensemen. He also played in his first NHL All-Star Game. In September 2019, he signed an eight-year, $64 million contract with the Senators. Established as one of the Senators' leaders, Chabot had 39 points (six goals, 33 assists) in 71 games in 2019-20. On Dec. 16, 2019, Chabot played 37:50 in ice time in a 4-3 overtime loss to the Tampa Bay Lightning, leading any other skater on the team by more than 11 minutes. It was the second-highest mark in ice time to Dennis Wideman, who played 38:05 in a shootout loss to the Vancouver Canucks for the Calgary Flames in 2014.

Chabot made the Senators out of training camp in 2016-17. But after playing in one game, against the Arizona Coyotes on Oct. 18, 2016, he was returned to Saint John of the Quebec Major Junior Hockey League.

Chabot started the 2017-18 season with Belleville, Ottawa's American Hockey League affiliate, but was called up after scoring seven points (two goals, five assists) in 13 games. The native of Sainte-Marie, Quebec, got his first NHL point on Oct. 13, 2017, with an assist in a 6-0 victory against the Calgary Flames. He scored his first NHL goal on Dec. 1, 2017, in a 6-5 victory against the New York Islanders. He also assisted on the game-tying and game-winning goals for his first multiple-point game in the NHL.

Internationally, Chabot helped Canada to a fourth-place finish at the 2018 IIHF World Championship, getting one assist in six games. In 2017, he had four goals and six assists in seven games to help Canada win the silver medal at the IIHF World Junior Championship. He was named the tournament's most valuable player and top defenseman.

Chabot capped a stellar junior career by leading Saint John to the QMJHL title and an appearance in the 2017 Memorial Cup tournament. He had 45 points (10 goals, 35 assists) in 34 games and was awarded the Emile Bouchard Trophy as the QMJHL's top defenseman. Chabot also had 23 points (five goals, 18 assists) in 18 playoff games and won the Guy Lafleur Trophy as the QMJHL's playoff MVP.

In 2015-16, Chabot had 45 points (11 goals, 34 assists) in 47 games for Saint John and was named to the QMJHL Second All-Star Team.