This article highlights two interlocking themes in moral and political philosophy in the Kantian tradition and examines their import for issues in international relations. First, I examine how constructivist interpretations of Kantian moral theory can inform an understanding of Kant’s Perpetual Peace and passages in other key texts that deal with international relations. Second, drawing on the constructivist tradition, I examine Kant’s remarks on the dependency of domestic justice on international justice. By bringing these two themes together, I put forward (...) a Kantian view of international relations that emphasizes the role of morality in resolving practical problems at the international level and draws attention to the ways in which solving problems of domestic justice is contingent on also solving problems of international justice. Each of these points provides a Kantian response to, and the second puts pressure on, realist views in international relations. (shrink)