2011-12: Alec Dillon played for the South Island Thunderbirds midget major hockey team in British Columbia — sharing the goaltending duties with future Victoria Grizzlies teammate Nic Reynard.
2012-13: Dillon played for the Westshore Wolves junior B team in the Vancouver Island Junior Hockey League as a 16-year-old. He posted a 3.96 goals against and .890 save percentage in 24 regular season games and had a 3.90 goals against and .892 save percentage in three playoff games.
2013-14: Dillon committed to playing college hockey at RPI in 2015-16 in September and skated for the Victoria Grizzlies in the British Columbia Hockey League, splitting time with the 19-year-old Reynard. He was 21-7-2 with 1 shutout in 33 games and had a 2.76 goals against and .910 save percentage. Victoria finished first in the Island Division and reached the playoff semifinals. Dillon played in nine playoff games and was 4-4 with 2 shutouts; posting a 2.56 goals against and .908 save percentage. Dillon was ranked 13th amongst North American goalies in the Central Scouting final rankings and was selected by Los Angeles in the fifth round (150th overall) of the 2014 NHL Draft.