This narrative review pursues an understanding of the relationship of libraries to the concepts of soft power and public and cultural diplomacy. The cross-disciplinary nature of the study required that the search approach include literature from both the International Relations and Library and Information Science disciplines. The analysed literature reveals three key gaps. First, research explicitly addressing the topic of ‘libraries and soft power’ is scarce. Second, the little Library and Information Science literature that addresses libraries and soft power rarely considers contemporary discourse. Third, the literature often has an implicit liberal institutionalist perspective, overlooking negative or hegemonic aspects of soft power. Given that soft power is considered increasingly relevant for representing national interests, understanding libraries’ roles and impact in international relations is significant and warrants further research.