As international tribunals close and the International Criminal Court struggles with jurisdictional issues and waning political support, national war crimes units — or specialized prosecution units — have emerged as important actors in the pursuit of international criminal justice. This article discusses three challenges these units face: (1) political and financial support, (2) access to and admissibility of evidence, and (3) coordination and cooperation within and among units. The article is based on an extensive literature review and interviews with forty-two current or former investigators and prosecutors at national war crimes units, international tribunals, and nongovernmental organizations.