2009-10: Sean Maguire skated for the North Island Silvertips in the British Columbia midget major league. Sharing the goaltending duties with Kolding Larson, he skated in 20 games for the fifth-place Silvertips – who earned their first playoff berth.
2010-11: Maguire had a strong first season for the BCHL's Powell River Kings as a backup to Quinnipiac University recruit Michael Garteig. He played in 15 games for the Kings and was 10-3 with two shutouts and had a 2.50 goals against and .903 save percentage. Powell River dominated the Coastal Division and reached the BCHL finals against Interior Division champion Vernon. Maguire made two appearances in relief of Garteig during the playoffs; allowing 1 goal on 16 shots in 44 minutes of action.
2011-12: Maguire had a breakout season – taking over as the starter in Powell River, backstopping Canada West to a championship in the 2011 U19 World Junior A Challenge, and committing to playing college hockey at Boston University in 2012-13. In 31 games for Powell River he was 17-12-1 with three shutouts and had a 2.33 goals against and .913 save percentage. In four games at the WJAC he was 3-1 with a 1.49 goals against and .942 save percentage. Canada West defeated Canada East in the championship game. Ranked 28th amongst North American goalies in Central Scouting's final rankings prior to the 2012 NHL Draft, Maguire was selected by the Penguins in the 4th round (113th overall).
2012-13: Maguire appeared in 21 games for Boston University as a freshman; starting all four games in the Hockey East tournament. Splitting the goaltending chores with fellow freshman Matt O'Connor, he finished the year 13-8 with 4 shutouts and had a 2.54 goals against and .926 save percentage. Boston University finished in a three-way tie for third in Hockey East and reached the championship game in the league tournament, falling to regular season champion Massachusetts-Lowell, 1-0. Maguire stopped 28 of 29 shots in the loss to the River Hawks.
Sean Maguire is a hybrid goaltender who possesses a solid frame and very good overall natural talent. He is fairly athletic with good lateral movement, but most importantly he is a winner. Maguire has a tendency to maybe overplay the puck or scramble around too much in his crease. He is considered raw at this point, but has the size and athleticism to potentially develop into an NHL caliber goaltender.
Maguire will play his sophomore season for Boston University where he will battle for starts.