Recent reporting and research by journalists and non-governmental organizations have described systemic flaws in investigations of civilian harm from U.S. military operations. New analysis has resulted in unprecedented Cabinet-level commitment to improve the Department of Defense’s approach to civilian harm, a commitment that led to the development of the Civilian Harm Mitigation and Response Action Plan. This Article argues that flaws in investigations undermine accountability for civilian harm and that the Department of Defense should improve investigation practices. In light of issues with investigation procedures, this Article discusses the relationship between civilian harm and alleged war crimes and applies international legal obligations and guidelines for investigations of alleged war crimes to U.S. investigation procedures. The Article assesses possible implications for complementarity under the Rome Statute and prosecutions of U.S. persons at the International Criminal Court. The Article closes with recommendations for improvement of investigation procedures.