What explains success and failure in internationally supported bureaucracies? This dissertation examines how the approaches of international actors strengthen or weaken bureaucratic effectiveness and democratic institutions after the 1999 NATO intervention in Kosovo. My research demonstrates that international actors face short-term trade-offs between supporting state-building and democratization. In order to build effective state bureaucracies, international actors need to insulate these bureaucracies from political and societal influences. By contrast, international actors can support the development of democratic institutions by promoting citizen mobilization and contestation, and therefore encouraging political and societal influences to shape, constrain and inform democratic decision-makers. Employing a comparative research design, this dissertation utilizes national survey data as well as data from 140 author-conducted interviews and focus groups collected over ten months of field work. While most research investigates the state as a unitary abstract actor, I disaggregate the state by contrasting its constituent bureaucracies that vary in effectiveness. I use three innovative sets of indicators to measure effective bureaucracies: mission fulfillment, penalization of corruption, and responsiveness to the public.