International law informs, and is informed by, concerns for global justice. Yet the two fields that engage most with prescribing the normative structure of the world order – international law and the philosophy of global justice – have tended to work on parallel tracks. Many international lawyers, with their commitment to formal sources, regard considerations of substantive (and not merely procedural) justice as ultra vires for much of their work. Philosophers of global justice, in turn, tend to explore the moral commitments of international actors without grappling with the international legal doctrine or institutions. In recent years, however, both disciplines have begun to engage with one another more. This discussion among international lawyers and philosophers addresses the promises of and challenges to interdisciplinary approaches to global justice. The contributors consider the added value of philosophical inquiry to issues facing international law practitioners or scholars, the salience of of international law for political philosophy, and the methodological distinctions between the two fields. The contributors also identify promising lines and examples of interdisciplinary scholarship.