2008-09: Dillon Donnelly skated for the Lac St. Louis Lions Midget AAA team in Quebec as a 15-year-old. He was selected by Moncton in the first round (16th overall) of the 2009 QMJHL Entry Draft and by Omaha in the fifth round (65th overall) of the USHL's Future Draft.
2009-10: Split time between the QMJHL’s Moncton Wildcats and Montreal Juniors, appearing in 51 games. He managed 3 assists to go along with 99 PIMS and a +4 rating, while going scoreless in 6 postseason matchups.
2010-11: Appeared in 63 games for the Shawinigan Cataractes of the QMJHL notching a goal and 7 assists. He also posted 153 PIMs and a -10 rating in the regular season before adding an assist and 12 PIMs in 9 playoff contests.
2011-12: Donnelly provided toughness and physical play on the blue line for the Memorial Cup champion Shawinigan Cataractes in his second junior hockey season. Donnelly led the Cataractes with 125 penalty minutes in 59 games and was plus-18 with 1 goal and 13 assists. Shawinigan finished first in the East Division and had the second best record in the QMJHL. The Cataractes were upset by Chicoutimi in the second round of the QMJHL playoffs but won the Memorial Cup championship as the host team. After missing the Cataractes' first round series due to injury, Donnelly was plus-2 with 1 assist and 16 penalty minutes in the Chicoutimi series. He skated in all six games at the Memorial Cup and was an even plus/minus with 21 penalty minutes.
Donnelly is not a flashy player, but he is great at what he does. The classic hard-nosed, crease clearing, defensive defenseman, he doesn’t have top four upside, but could very well develop into a bottom pairing, penalty killing, physical presence on the blueline.
Donnelly was a member of the Memorial Cup champion Shawinigan Cataractes in 2011-12, and will continue his junior career with that club in 2012-13.