Abstract This article examines the role of the International Organization for Migration (IOM) and the United Nations High Commissioner for Refugees (UNHCR) in the implementation of the European Union (EU) migration and asylum policy in Niger. Building on policy analysis and qualitative interviews with stakeholders, it contributes to the literature on the externalization process of EU borders. The first part of the article focuses on the international and local context in which this process has taken place in Niger since 2015. The second part refers to the principal-agent (PA) theory inspired from economics to model the dynamics of the delegation relationships linking the European Commission (EC) to the IOM and the UNHCR in Niger. It is argued that the two main objectives pursued by the EU through the externalization of its migration and asylum policy—namely the offshoring of border control and the outsourcing of asylum claims processing—are respectively fulfilled by the IOM and the UNHCR in Niger. As such, this article highlights how the cooperation of International Organizations (IOs) is critical to enable the EU to filter and restrict human mobility from the Sahel region.