The law of international organizations is often described in terms of both its universality and its unity. Writers in this field begin their texts with an acknowledgement that there are common legal principles that have been developed by, and can be applied to, a variety of international organizations. The idea that there are legal principles applicable to multiple organizations – whatever their membership, location, powers, technical functions, or financial resources – is also implicit in the reports of the International Law Commission discussing the immunities, responsibilities, and law-making capacity of international organizations. But despite this search for common principles, a question remains whether international institutional law is based on the practice of all, or at the very least, a range, of organizations. Writers in this field have tended to focus on the activities of organizations based in either Europe or North America, including the United Nations and its specialized agencies, the European Union, and Council of Europe. This article argues that the omission of the principles and practices of organizations outside Europe and the United Nations’ system, specifically Asia Pacific organizations, undermines the claim of international institutional law to be universal. It explores the way in which a more inclusive approach – one that pays attention to the perspectives of Asia Pacific organizations – could illuminate certain features of the law and lead international lawyers to reconceive some of its central principles.