Aaron Gillmor has been competing in international races since 2009, initially in the junior classes. He took part in the 2009 Biathlon Junior World Championships in Canmore and won the silver medal in his Canadian homeland alongside Kurtis Wenzel and Scott Gow behind the relay from France and ahead of Russia. He also finished 31st in the sprint and 25th in pursuit and individual. A year later he finished 51st in the individual, 58th in the sprint, 40th in the pursuit and eight with the relay in Torsby . Gillmor was very successful at the Canadian Biathlon Championships 2011 in Charlo , where he won all four titles in the individual, sprint, pursuit and mixed relay in the juniors. At the North American Championships in Summer Biathlon 2010 in Canmore, he took part in an international men's championship for the first time and reached seventh place in the sprint and ninth in the pursuit race in the roller-ski competitions .
Gillmor has also been taking part in cross-country skiing in international competitions since 2009, initially in lower-class races such as the Nor-Am Cup , but also in national Canadian championships, but without achieving any results worth mentioning. In Otepää he took part in the Nordic Junior World Ski Championships in 2011 and was 68th in the 10-kilometer freestyle, 75th in the classic sprint and ninth in Canada's relay.