Intersections exist regarding how institutions and individuals respond in the wake of mass violence, and we explore one theoretical perspective: resilience—the ability to overcome in the face of adversity. By controlling for the institutional context, we analyze the microlevel impact of testifying on witnesses who testify. New survey data provide information from 300 prosecution, defence, and Chambers witnesses who appeared at the International Criminal Tribunal for the Former Yugoslavia. We test propositions about resilience related to trauma, motivations, contributions to justice, fair treatment, witness fatigue, and human security. Witnesses who experienced greater trauma, who were more highly motivated, who believed they contributed to justice, and who were satisfied with their current situation were more positive about testifying. Those who believed they were treated fairly by prosecution and defence were less negative. The findings add to the debate about the burden of bearing witness in post-conflict societies and why some overcome adverse experiences related to mass violence.