International organizations (IOs) in policy implementation face a major functional dilemma. On the one hand, their country-level offices require significant local knowledge to adjust abstract policies to local conditions. The most straightforward way to gather such knowledge is by employing local staff who are nationals of the host state. On the other hand, previous studies indicate that conflicts of interest between mission objectives and the interests of an employee’s home government are more pronounced for local staff. Local staff thus constitute a risk to the impartiality of IOs, which is an important asset. Drawing on survey research among a large number of IO field offices from different organizations, this paper studies how missions vary in navigating the ensuing tension and what impact local staff have on the implementation of IO mission mandates.