Addressing global health challenges requires complex coordination and collaboration between actors, often through the process of Global Health Diplomacy (GHD). Although considerable scholarship argues the importance of improving this process to build better health policies and systems, few studies have investigated the 'health diplomats' directly leading this work. In this study, we seek to better understand GHD from a practitioners' view by exploring perceptions of knowledge acquisition, capacity building, and network development amongst those who coordinate and orchestrate global policy solutions. Taking an inductive qualitative approach, we conduct interviews of 54 experienced GHD professionals working across government, civil society, and private industry in 23 countries and identify key themes that outline challenges and opportunities for capacity building in GHD. Findings indicate a nascent global community bound by shared identity and motivations, but also hurdles regarding the transfer of tacit knowledge, network integration, and the improvement of institutional leadership. These findings highlight the boundaries by which knowledge and capacity are difficult for health diplomats to acquire or transfer, which help explain limitations to achieving better outcomes for global health. Further, this study may assist scholars and practitioners' work by considering GHD as a purposeful community of practice.