We develop and test a theory of the supply side of third-party conflict management. Building on Kydd’s (2003) model of mediation, which shows that bias enhances mediator credibility, we offer three complementary mechanisms that may enable mediator credibility. First, democratic mediators face costs for deception in the conflict management process. Second, a vibrant global democratic community supports the norms of unbiased and nonviolent conflict management, again increasing the costs of deception for potential mediators. Third, as disputants’ ties to international organizations increase, the mediator’s costs for dishonesty in the conflict management process rise because these institutions provide more frequent and accurate information about the disputants’ capabilities and resolve. These factors, along with sources of bias, increase the availability of credible mediators and their efforts to manage interstate conflicts. Empirical analyses of data on contentious issues from 1816 to 2001 lend mixed support for our arguments. Third-party conflict management occurs more frequently and is more successful if a potential mediator is a democracy, as the average global democracy level increases, and as the disputants’ number of shared International Organization (IO) memberships rises. We also find that powerful states serve as mediators more often and are typically successful. Other factors such as trade ties, alliances, issue salience, and distance influence decisions to mediate and mediation success. Taken together, our study provides evidence in support of Kydd’s bias argument while offering several mechanisms for unbiased mediators to become credible and successful mediators.