In a global pandemic, public health outcomes are not the only variables at stake. Also at stake are countries' nation brands and influence, which hinge on how a country responded to the crisis. Based on a case study of a middle power, South Korea, one of the more successful COVID-19 national responses so far, we offer an exploratory conceptual explication of pandemic public diplomacy that is grounded in a normative framework of substance, information, trust, collaboration, and mutual benefit. Sentiment analyses of social media and international news media suggest that the country is perceived as a model on how to cope with the pandemic by international audiences. Unlike other public diplomacy contexts, pandemic public diplomacy challenge conventional assumptions about public diplomacy and nation branding. As nation-states confront a common enemy, how public diplomacy and nation branding play out in COVID-19-arguably the most socially disruptive event in modern history-helps to shed light on the dynamics of mutual interdependence in an interconnected yet competitive world fraught with fear, uncertainty, and information deficiency.