Effectively managing the Canada-US border has emerged as a major security challenge post-9/11. Burden-sharing theories suggest that the United States would take the lead on border security due to its hegemonic role in ensuring North American security, while smaller nations such as Canada free-ride. The authors refute the free-rider hypothesis and propose an approach which accounts for the differentiated concerns held by contiguous states. By dedicating sizeable resources to the issue of border security and by appealing to advantageous negotiation strategies, Ottawa has leveraged its position as a secondary state vis-à-vis the United States. Efforts employed by the province of Québec have bolstered Canada’s relative influence in this issue area. The authors argue that Québec and Ottawa perceived and acted on complementary interests which empowered the Canadian government to respond more forcefully to US-driven border security measures after 9/11. We conclude with alternative models to border security management, as well the practical implications of our argument.