One of the NHL's top defensemen, Subban was selected by the Montreal Canadiens in the second round (No. 43) of the 2007 NHL Draft.

Before turning pro, Subban played four seasons for Belleville of the Ontario Hockey League. He played in the OHL All-Star Game in 2007-08 and led all defensemen in playoff points (23) that season. He also helped Canada win a gold medal at the 2008 World Junior Championship.

Subban tied for the scoring lead among defensemen at the 2009 World Junior Championship with nine points, had a tournament-best plus-12 rating and was named a tournament all-star as Canada won gold again. He was captain of the Eastern Conference at the OHL All-Star Game in 2008-09 and was named to the OHL First All-Star Team. He had 62 assists and 76 points, finishing as runner-up for the Max Kaminsky Award, given to the league's top defenseman.

Subban joined the Canadiens' American Hockey League affiliate in Hamilton for 2009-10 and was third among league defenseman with 53 points. He was named to the AHL First All-Star Team and the AHL All-Rookie Team.

Subban made his NHL debut Feb. 20, 2010, against the Philadelphia Flyers and got an assist. He played in two NHL regular-season games and 14 Stanley Cup Playoff games, getting a goal and eight points in the postseason.

Promoted to the Canadiens for 2010-11, Subban had 14 goals and 38 points and led Montreal with nine power-play goals. In 2011-12 he led the Canadiens in total ice time on the power play (283:04), total ice time (1,968:28) and average time on ice (24:18). On March 20, 2011, against the Minnesota Wild, Subban became the first Canadiens rookie defenseman to have a hat trick.

Subban won the Norris Trophy as the League's top defenseman and was named to the NHL First All-Star Team in 2012-13, tying for the NHL scoring lead for defensemen (38 points). Subban also tied for second in the NHL with 19 power-play assists and tied for the Montreal playoff scoring lead with four points.

Playing all 82 games for the first time in 2013-14, Subban had 53 points. In 2014-15 he was tied for second among NHL defensemen with 60 points and second at his position with 45 assists. He also led the Canadiens in average time on ice (26:12).

In 2015-16, his last season in Montreal, Subban led the Canadiens in assists (45) and average time on ice (26:22, fifth in the NHL). On June 29 2016, the Canadiens traded Subban to the Nashville Predators for Shea Weber.