He also previously played for the Vegas Golden Knights, Chicago Blackhawks, Buffalo Sabres, and Columbus Blue Jackets.

His younger brother, Jordan, was selected in the fourth round by the Vancouver Canucks during the 2013 NHL entry draft and currently plays for the Dornbirn Bulldogs of the Austrian Hockey League (EBEL).

After switching to goaltender, he began playing in the Midget AAA level Greater Toronto Hockey League.

[1] Subban was selected in the 11th round of the 2009 Ontario Hockey League (OHL) priority draft by the Belleville Bulls.

[4] Due to the 2012–13 NHL lockout, Subban spent the season with Belleville, appearing in 46 games with a record of 29–11–4 and .923 save percentage.

In the preseason schedule, Subban had his first opportunity to face his defenceman brother P. K. on the Montreal Canadiens squad on September 16, 2013, in a preseason match between the teams at Montreal's Bell Centre — Malcolm replaced Bruins rookie goaltender Chad Johnson at about 14 minutes into the game's second period, and managed to stop every shot in the 31:49 he played in-net, en route to a 6–3 defeat of the Canadiens.

[12] He was cut shortly after appearing in a preseason game where he allowed eight goals to the Detroit Red Wings, and assigned to Boston's American Hockey League (AHL) affiliate in Providence.

[24] He was placed on waivers on October 2, 2017, during the Bruins training camp after failing to beat Khudobin for the team's backup goaltender position.

[26] He made the Golden Knights out of training camp and was the backup goalie for team's inaugural game, a 2–1 victory over the Dallas Stars on October 7.

[30] On November 17, Subban was taken off injured reserve and was the backup for Maxime Lagacé in the following game against the Los Angeles Kings.

[35] In the 2019 off-season, he filed for salary arbitration, but signed a one-year contract with Vegas before the hearing could take place.

[38][39] In the following off-season, due to salary cap considerations, Subban was not tendered a qualifying offer by Blackhawks on October 8.

[43] Entering his third season with the Blackhawks in 2021–22 and with the acquisition of starting goaltender Marc-André Fleury, Subban was placed on waivers and reassigned by Chicago to AHL affiliate, the Rockford IceHogs.

[44] With three goaltenders on the roster competing for ice time with the IceHogs, Subban featured in only five games, collecting two wins, through the opening two months of the season.

He made his debut with the Sabres, allowing six goals on 25 shots before he was pulled in the third period of a 6–2 defeat by the Carolina Hurricanes on December 4.

[47] On January 12, 2022, Subban made a relief appearance against the Tampa Bay Lightning in place of the injured Ukko-Pekka Luukkonen.

He underwent surgery, and Sabres' head coach Don Granato speculated Subban would miss the remainder of the season.

[48][49] On April 29, while recovering from season-ending surgery, Subban sang "The Star-Spangled Banner" during a Sabres home game against the Chicago Blackhawks.

[51] Due to another logjam of goaltenders in Buffalo's system, Subban again ended up in the AHL with the Sabres' affiliate Rochester Americans for the 2022–23 season.

[7][52] The Americans made the 2023 Calder Cup playoffs and helped the team reach the Eastern Conference finals where they were defeated by the Hershey Bears.

Approaching the 2024–25 season, Subban was signed to a professional tryout (PTO) with the Grand Rapids Griffins of the AHL, primary affiliate to the Detroit Red Wings, on October 7, 2024.