Abstract
Establishing climate services within health systems is increasingly recognized as essential for strengthening resilience in low- and middle-income countries, yet little is known about how such efforts gain legitimacy. This case study examines the early-stage establishment of climate services within Uganda's national health system through the DHIS2 digital health platform. Drawing on legitimacy theory and boundary object theory, we trace how actors mobilized pragmatic, moral, and emerging cognitive forms of legitimacy, and how the platform mediated these processes. We introduce the notion of digital health platforms as legitimacy infrastructure-socio-technical arrangements through which legitimacy is constructed, transferred, and normalized across institutional boundaries. The study identifies key legitimacy-building mechanisms, including co-creation practices that foster ownership, alignment with national policy priorities that secure institutional backing, and the use of trusted digital infrastructures that lower adoption barriers. By theorizing how platforms mediate cross-sectoral acceptance, the study contributes knowledge of why some innovations move from establishment toward institutionalization while others falter. For policymakers and implementers, this case-study underscores the importance of embedding co-creation, aligning innovations with national frameworks, and establishing cross-sector collaboration early in the establishment of climate services for health, particularly when anchored in existing health information infrastructures.