Faith and religion have long been recognised as a dynamic force in the international system. Within the scope of Diplomacy Studies, however, the positive integration of faith into the theory and practices of diplomacy is only a recent endeavour. Faith-based diplomacy, which emerged in the 1990s, is a framework for achieving this effective integration. This thesis evaluates the theoretical constructs of faith-based diplomacy to assess if these frameworks are appropriate when addressing the challenges of the 21st Century. Given the changing nature of conflict, the implications of globalisation, and the impacts of global terrorism and religious violence, this thesis finds that the current theoretical frames are insufficient. As such, this thesis aims to reconceptualise the framework of faith-based diplomacy considering the theoretical advancements in Diplomacy Studies, and the changes in the international system since the faith-based diplomacy’s introduction into scholarship. A comprehensive review of the literature in Diplomacy Studies reveals that faith-based diplomacy can benefit from the expanded scopes of analysis, including areas such as public diplomacy and cultural diplomacy. This, along with the development of concepts such as reconciliation, mediation and the tracks of diplomacy all suggest that the theoretical framework of faith-based diplomacy can be improved. To expound on this improvement, this thesis evaluates the development of theory in Diplomacy Studies more broadly, recognising the presence of faith and religion in diplomatic theory through history. This thesis, however, will also assess the actors who engage with diplomacy, highlighting ways in which faith-based diplomacy can be utilised by both state and nonstate actors. In doing so, this thesis provides an evaluation of faith-based diplomacy in theory, and also in terms of how actors in the contemporary international landscape may be able to engage in practice. From this evaluation, this thesis concludes with key recommendations on how faith-based diplomacy’s framework can be reconceptualised to integrate more effectively the assets of religion into the practice of diplomacy. This reconceptualisation contributes to the growing body of scholarship within Diplomacy Studies by providing a theory that better reflects the nature of diplomatic theory and practice in the current international system.