[5] Chabot attended the Senators' 2015–16 rookie and main training camps after taking part in Hockey Canada's National Team Summer Showcase held in Calgary during late-summer, playing in three preseason games with Ottawa.

[6] A year later, Chabot attended the Senators' 2016–17 training camp and made the team, making his NHL debut on October 18, 2016, versus the Arizona Coyotes.

[12] Following the season, hockey writers began listing Chabot as one of the NHL's top defensemen,[12] and in September 2019, he signed an eight-year, $64 million contract extension with the Senators.

In the 2021–22 season he averaged 26:23 minutes of ice time per game, the highest for any player on any team in the league, until a March 16, 2022, hand injury caused by Columbus Blue Jackets forward Sean Kuraly ruled him out for the remainder of the year.

[16] During the 2022–23 season, Chabot struggled, with growing criticism of his game, though some argued that injury and overuse have affected his play.

[20][21] On December 1, 2015, Chabot was invited to the Team Canada selection camp for the 2016 World Junior Hockey Championships.

[23] Chabot was selected as an alternate captain for Team Canada at the 2017 World Junior Ice Hockey Championships.