2009-10: Adam Pelech played for the Toronto Marlboros minor midget AAA team in the GTHL. In 69 games he scored 6 goals with 28 assists. Pelech was selected by the Erie Otters in the second round (22nd overall) of the 2010 OHL Priority Draft.
2010-11: Pelech skated in 65 of 68 games for Erie in his first OHL season and played for Canada Ontario in the 2011 U17 World Hockey Challenge. He was plus-14 and scored 1 goal with 12 assists and had 27 penalty minutes. The Otters finished third in the Midwest Division and lost to Windsor, the defending Memorial Cup champion, by one goal in the deciding seventh game of an epic first round series. Pelech played in all seven playoff games, three of which went to overtime, and was minus-four with 2 assists and 2 penalty minutes. Skating for gold medal-winning Canada Ontario at the WHC tournament, he had 1 assist and 2 penalty minutes in five games.
2011-12: Pelech was limited to 44 games due to a wrist injury as Erie won just ten games during the regular season. At the end of the season Pelech represented Canada at the 2012 U18 World Junior Championship after Erie failed to reach the OHL playoffs. Pelech scored 2 goals with 18 assists and was minus-20 with 52 penalty minutes as the Otters had the OHL's worst record. Playing for Canada, which defeated Finland in the U18 bronze medal game, Pelech was plus-2 with 8 penalty minutes in seven games. He was ranked 54th amongst North American skaters at mid-season and slipped to 120th in Central Scouting's final rankings prior to the 2012 NHL Draft and was selected by the Islanders in the third round (65th overall).
2012-13: Pelech played 59 games for Erie in his third OHL season — overcoming an early season wrist injury which kept him out of the tryout camp for Canada's U20 team. He led Otters' defensemen with 40 points, scoring 8 goals with 32 assists, and was -16 with 98 penalty minutes. Erie finished last in the Midwest Division with the OHL's second-worst record.
Pelech will play for the Erie Otters of the OHL for the 2013-14 season.