Governance institutions such as the Arctic Council face ongoing (de)legitimation that impacts the broader legitimacy beliefs which enable them to govern effectively. Research has increasingly studied how different actors engage in legitimation and delegitimation that bolster or challenge legitimacy, but there has been limited study of the variation in the (de)legitimation practices of individual states and the reasons for this variation. This article studies variation in discursive (de)legitimation of the Arctic Council by the United States and China. It advances a theoretical argument for how this variation in (de)legitimation is driven by broader political developments. Using content analysis, it maps these two states’ (de)legitimation of the Arctic Council over a 12-year period and examines evidence for this theory. The article finds that both states vary considerably in their (de)legitimation of the Arctic Council over time. Changes in the intensity of their (de)legitimation are found to be linked to political developments including heightened security tensions, positive/negative shifts in environmental politics, and institutional changes. This contributes empirical evidence and new theoretical insights to the body of research about how different actors engage in (de)legitimation of global governance.