Global health diplomacy (GHD) describes the practices by which governments and non-state actors attempt to coordinate and orchestrate global policy solutions to improve global health. As an emerging field of practice, there is little academic work that has comprehensively examined and synthesized the theorization of Global Health Diplomacy (GHD), nor looked at why specific health concerns enter into foreign policy discussion and agendas. With the objective of uncovering the driving forces behind and theoretical explanations of GHD, we conducted a critical literature review. We searched three English-language scholarly databases using standardized search terms which yielded 606 articles. After screening of abstracts based on our inclusion/exclusion criteria, we retained 135 articles for importing into NVivo10 and coding. We found a lack of rigorous theorizing about GHD and fragmentation of the GHD literature which is not clearly structured around key issues and their theoretical explanations. To address this lack of theoretical grounding, we link the findings from the GHD literature to how theoretical concepts used in International Relations (IR) have been, and could be invoked in explaining GHD more effectively. To do this, we develop a theoretical taxonomy to explain GHD outcomes based on a popular categorization in IR, identifying three levels of analysis (individual, domestic/national, and global/international) and the driving forces for the integration of health into foreign policy at each level.