While long overlooked, power is central to understand how actors engage in global health policymaking. We reviewed how the Japanese and Indonesian governments exerted power and engaged in global health diplomacy during negotiations to conceptualize the post-2015 Sustainable Development Goal for health (SDG3). We conducted deliberative policy analysis including semi-structured, in-depth, interviews with more than 71 policymakers, which we analyzed adapting Barnett and Duvall's power framework. We find that both Japan and Indonesia exerted non-material power (institutional, productive and structural power) to advance largely domestic political interests. Japan's government mainly exerted institutional power, leveraging relationships within the World Bank and the World Health Organization, whereas Indonesia's government focused on structural power, with its president serving as co-chair of the UN Secretary-General's High-Level Post-2015 Panel. Our analysis suggests that the ways in which states engage in global health diplomacy is shaped by the relationship between different intra-state institutions, particularly the Ministry of Foreign Affairs and the Ministry of Health, and is further determined by broader foreign policy and diplomatic priorities. We find that the decline of states' influence is over-stated: states continue to exercise significant power in global health diplomacy, pursuing domestic political imperatives and strategies to improve population health. As states expand their global health engagement, researchers should seek to better understand how states participate in an increasingly crowded and contested global health field.