With the end of the Cold War and the collapse of the bipolar system in international relations, the concept of international peace has undergone profound transformations, experiencing new dynamics and variables. According to this study, since the 1990s, the notion and practice of international peace have faced a highly critical and precarious situation. The mechanisms designed to ensure peace including the United Nations preventive diplomacy as the exclusive institutional framework for maintaining international peace have largely failed in preventing armed conflicts and large-scale genocides, especially when compared to the Cold War era. This research raises the key question: How can the performance of the United Nations preventive diplomacy in the post-Cold War period be evaluated? The hypothesis proposed in response is that the UN’s preventive diplomacy in the post-Cold War era has not been successful in achieving international peace, primarily due to its weaknesses and ineffectiveness in resolving armed conflicts.