2009-10: Selected in the 11th round (218th overall) by Belleville in the 2009 OHL Priority Draft, Subban appeared in one game with the Bulls, and played in two junior games with the CCHL's Toronto Junior Canadiens – spending most of the season with the Mississauga Reps. The Reps captured the GTHL championship and reached the final game of the 2010 Telus Cup (Canada's midget AAA hockey championship). Subban recorded two saves in 13 minutes of action in his lone appearance with the Bulls and was 0-1 with a 3.39 goals against and .882 save percentage in two games with the Junior Canadiens. Subban split time with Santo Provenzano for the Reps and was most impressive in the Telus Cup championship game, stopping 55 shots in a 3-2 loss to the Notre Dame Hounds. In 14 regular season games he had a 1.86 goals against and in 7 playoff contests was at 2.00 goals against. In five Telus Cup contests he was 2-2-1 with a 3.07 goals against and .921 save percentage.
2010-11: Subban played in 32 games for Belleville, being named to the OHL's All-Rookie Team, and represented Canada at the 2011 U18 World Junior Championship. Playing on a Bulls team that finished with the league's third-worst record, he was 10-17-2 with a 3.16 goals against and .900 save percentage. The Bulls reached the playoffs by finishing three points ahead of Peterborough in the East but were swept by Mississauga St. Michael's. Subban started three of four games in the playoffs, and had an impressive .933 save percentage and 2.02 goals against despite going 0-3. Subban appeared in five of seven games for fourth-place Canada at the U18 WJC and was 3-2 with two shutouts; finishing with a 2.98 goals against and .913 save percentage.
2011-12: Subban skated in 39 games for Belleville in his second season; being hampered by a mid-season groin injury. He was one of the OHL's top goaltenders and a big part of the Bulls turnaround as Belleville finished second in the East Division. He finished with a 25-14 mark and recorded three shutouts with a 2.50 goals against and .923 save percentage. In the Bulls' six-game playoff season with eventual OHL runners-up Ottawa he was 2-4 with one loss coming in overtime and had a 2.93 goals against and .917 save percentage. Subban was invited to the NHL Draft Combine and was the top ranked North American goalie in Central Scouting's final rankings (up from 20th in the mid-term rankings) prior to the 2012 NHL Draft.
Malcolm Subban is an athletic goaltender with size and explosive lateral mobility. Practically unbeatable in one-on-one situations, he’s poised but is also capable of making highlight reel saves thanks to his athleticism and agility. Possessing NHL bloodlines, Subban is charismatic, but in a more understated way than his infamous older brother. However, Subban has drawn some criticism for his technique which is less refined than other goalies in his situation that have been at the position longer. If Subban can iron out the wrinkles in his technique, he has star potential.