Distinctive institutional features can make a regime particularly suited for conducting one or more generic tasks of governance: building knowledge, strengthening norms, enhancing problem-solving capacity, or enforcing rule compliance. Each of those governance tasks constitutes a potential “niche” that a regime can specialize in within a larger institutional complex. Applying this niche-oriented approach to the case of Arctic marine transport helps to explain the emerging division of labor between regional and global institutions in an issue area marked by rapid change. Drawing on earlier regime-effectiveness research, the article examines the potential of regional institutions, especially the Arctic Council, to contribute to strengthening the international governance system for shipping, based on the UN International Maritime Organization (IMO). Although the Arctic Council is not well positioned to regulate regional shipping activities, it may facilitate regulatory advances in the IMO, in part by knowledge-building and in part by helping Arctic states to find common ground on matters of controversy. The Council is also well equipped to enhance regional maritime infrastructure, like capacities for responding to oil spills, and search and rescue operations. Should binding region-specific international rules on Arctic shipping be adopted, Arctic institutions could play a role in coordinating port-state enforcement measures—but existing institutions with broader participation are better suited and will probably remain dominant. The larger question of achieving cross-institutional interplay that can promote effectiveness is relevant in any region or issue area, because efforts to solve specific problems usually involve more than one institution.