Expert organizations in nature conservation are often described as boundary organizations that facilitate science-policy interfaces. Besides the boundary between science and policy, boundary organizations need to manage other social boundaries, such as between different knowledge forms and between different categories of actors. In order to shape credible, legitimate, and policy relevant knowledge a boundary organization has to make use of competences from both sides of these boundaries. However, this boundary management is to a large extent concealed for those external to it. Focusing the Intergovernmental Science-Policy Platform for Biodiversity and Ecosystem Services (IPBES), this study explores how boundaries are created and managed, as well as how they become important in order to shape credible, legitimate, and policy relevant knowledge. In particular, three boundaries are analyzed: between science and policy, between scientific knowledge and indigenous and local knowledge, and between senior and young experts. Three questions are central; how are boundaries created and managed in the process of knowledge production?; how does boundary work on different boundaries in the same organization intersect and influence one another?; how is boundary work important, and what role does it play for the production of policy relevant knowledge? The empirical material consists of official documents from IPBES and interviews with IPBES fellows. By showing how different boundaries intersect in the construction of expert knowledge, this study deepens the understanding of the preconditions for expert-based policy recommendations in nature conservation.