Mediation has become a dominant method of peaceful conflict resolution in the international system. Since the end of the Cold War in particular, an increasing number of belligerents have relied on mediators to help end their disputes. Yet, while mediators offer many advantages in the process of making peace, at times serving as the only way for rivals to move forward, mediation may also entail negative, unintended, consequences. Escalation of the conflict upon the mediator’s entrance is one such unintended consequence. Strategic considerations on the one hand, and psychological mechanisms on the other, frequently prompt rivals to escalate rather than cease hostilities upon the onset of mediation. Another possible unintended consequence is prolongation of the conflict due to the presence of the mediator. With a mediator involved in the negotiations, rivals may be tempted to put off an agreement in the hope of gaining a better deal while evading the cost of all-out conflict, or the disputing parties may conclude that they stand to gain more from the mediation process itself than from reaching a settlement. Mediation may also lead to fragile settlements that are prone to be short-lived as compared to settlements arrived at by the disputing parties on their own. This process is driven by factors such as the tendency of mediators to push for settlement terms that are easily attainable but that do not resolve the underlying causes of the conflict and are not necessarily sustainable. Whereas the contribution of mediation to conflict resolution is widely researched and discussed by scholars, to fully appreciate the significance of mediation as a method of conflict resolution, it is crucial to understand its possible negative consequences as well. A clear understanding of the full picture is essential for scholars and practitioners alike.