Conflict prevention is enjoying a renaissance in international policy circles. However, the official machinery of the international community presently offers few institutions with a specific mandate to address the causes of political violence at an early stage. One such multilateral mechanism dedicated solely to the prevention of conflict is the High Commissioner on National Minorities (HCNM) of the Organization for Security and Co-operation in Europe (OSCE). Over two decades, the office has developed a significant track record of effectiveness against which to examine the preventive efforts of other intergovernmental organizations. In this article, we examine the prevention efforts of the HCNM in Georgia, Macedonia, and Ukraine and compare these with the preventive diplomacy of three other intergovernmental organizations (IGOs): the Organization of American States (OAS) in Guyana, the Commonwealth in Fiji, and the UN in Afghanistan, Burundi, and Macedonia. Our findings offer some useful and surprising insights into effective prevention practice, with implications for how IGOs might improve preventive diplomacy in the future. © 2012 Koninklijke Brill NV, Leiden.