The global governance of borders and migration is increasingly carried out by intergovernmental organisations. Organisations like the IOM epitomise this trend, and with the backdrop of ‘migration crisis’ govern mobility by deploying humanitarian assistance as much as by providing border security expertise. This article argues that we should pay attention to the ways the IOM brings together these seemingly distinct rationales and practices of care and control. It argues that the IOM can be understood as a ‘developmental borderwork’ actor, whose practices are underpinned by a sincere but procedural humanitarianism, a technical focus on best practices and implementation, and an intervention approach drawn from the development industry. To make this argument, the article draws from two empirical trends. First, it examines IOM projects building new border infrastructures and technologies in Mauritania and South Sudan, seeing in these a fusion of security and statebuilding. Second, the article traces the organisation’s development of a humanitarian border management (HBM) concept through which it works to reconcile its emerging migrant protection self-image with member states’ security needs. Each of these cases reflect the tensions within the IOM between humanitarianism, statebuilding, and the persistent reality of state sovereignty.