This article raises the question of how the evolution of constitutional structures in international history can be conceptualized and narrated. This question is nurtured by the divergent historical accounts found in the literature on global constitutionalism and the historical-comparative literature on international societies. Although both literatures have so far largely ignored each other, they share a number of common conceptual problems and should therefore engage in a dialogue. The article sketches out the contours of such a dialogue to reveal the insufficient sensitivity of both literatures to the historicity of constitutional structures as well as their inherent political dimension. This article proposes to conceptualize constitutional structures as a set of fundamental and prioritized principles and rules that serves as a framework for the self-ordering of relations between polities. It thereby differentiates between a meta-constitutional and a legal-constitutional dimension and proposes seven analytical tools for more nuanced and empirically sensitive constitutional histories of interpolity relations. Such a historical perspective helps to account for the conditions of emergence as well as to delineate the novelty of contemporary global constitutionalism.