Abstract Global public–private partnerships (PPPs) have become prominent in efforts to address global challenges, particularly in the health field. In the scholarly literature, global PPPs have been conceptualized as arenas for voluntary public–private cooperation rather than agents of global governance. This paper challenges this approach, arguing that a sub-class of highly institutionalized partnerships have developed into transnational bureaucracies that, much like international organizations, can draw from their administrative capacities to exercise agency and gain and consolidate authority over time. To substantiate this argument, I present an in-depth analysis of five global health partnerships that played a leading role in the Access to Covid-19 Tools Accelerator (ACT-A), the initiative that sought to coordinate the global response to covid-19. Based on extensive document review and analysis of the ACT-A PPPs —Gavi, the Vaccine Alliance, The Global Fund to Fight AIDS, Tuberculosis and Malaria, The Coalition for Epidemic Preparedness Innovation, Unitaid, and The Foundation for Innovative New Diagnostics — I show how these partnerships’ leadership role during the pandemic emerged from a decade long build-up of PPP agency. These organizations gained administrative capacities that enabled them to increase their authority vis-à-vis their donors, boards, and other external actors through three interlinked strategies: (a) developing greater financial autonomy; (b) expanding their mandates (including toward pandemic preparedness and response); and (c) establishing inter-partnership cooperation and mutual representation to other forums. My analysis suggests the need for future research to consider highly institutionalized PPPs as agents of global governance and to explore empirically and theoretically the consequences of their rising authority.