IUCN, an IGO-NGO hybrid, is world’s largest organization on biodiversity conservation. The international legal status of IUCN is unique and its network of epistemic communities plays a crucial role in the development of international biodiversity law. This article discusses the unique and crucial influence that IUCN has over the development of international law relating to biodiversity conservation: Part One will introduce certain unique features of IUCN. Part Two will explore the importance of IUCN on the global biodiversity governance system, and part Three will discuss the contribution of IUCN’s Epistemic Community Network in the development of international law.