A sharp rise of public-private partnerships is changing the way the United Nations and other public international organizations work. Organizations eagerly embrace wealthy, experienced partners, such as major foundations and corporations, in order to fund ambitious projects. But safeguards against potential problems have not kept pace with partnership activities. Looking to fundamental principles of public choice and political economy well-known in the U.S. administrative law context, this Article develops a multifaceted notion of “partner capture” to describe the dangers of this expansion in partnership activities for the U.N. and similar organizations. The dangers include agenda distortion, intra-organizational rivalries, reputational damage, and financial liability. In light of these challenges, the Article proposes a structural solution for these problems in the form of an Office of Independent Review. Such an office would play a restrictive gatekeeper role but could also stimulate new project ideas to fulfill an organization’s goals efficiently. Leveraging the expertise and credibility built by the office would place the international organization – and not its private partners – in the role of primary agenda-setter. In the end, preventing partner capture illustrates one way in which international law can become more effective by drawing on domestic analogues and establishing new accountability structures.