The literature on ethnic kin-groups primarily focuses on their role in perpetuating conflict. Less attention has been devoted to how ethnic kin-groups might encourage mediation in disputes affecting their kin in other nations. We argue that transborder kin-groups’ collective concern for the welfare of their fellow members in other states can motivate interstate mediation efforts. Utilizing the Ethnic Power Relations and the Issue Correlates of War datasets, we examine how transborder kin-group connections shape the likelihood of mediation, as well as who provides it. Our findings suggest that the deeper the network of transborder kin-group connections among target states of territorial disputes, the more likely mediation is to occur. Alternatively, challenger transborder kin-group connections reduce the likelihood of mediation. While transborder kin-group connections help explain the likelihood of mediation, mediation is often not provided by the connected third-party state. Instead, these connections promote mediation from international organizations, particularly regional organizations.