As planetary health thinking has become a dominant scientific paradigm, epidemiologists who seek to inaugurate it as a field claim its revolutionizing awareness for “the health of human civilization and the state of the natural systems on which it depends” in an anthropogenic era (Whitmee, 2015). However, the concept’s recent institutionalization as the Planetary Health Alliance (“PHA”) places it within the legacy of the Rockefeller Foundation (“RF”), which has played a critical role in Global Health, further complicates any understanding of the field's distinction in governance practices and authorizing narratives. While philanthropy has historically enabled investments in international and global health, the medical and financial procedures involved play a significant role in the practice and politics of what it means to think and act on a planetary health scale. By assembling a critical genealogy of planetary health, I interrogate the gaps between its emergent reality and its moral, political, and medical aspirations. Drawing from scholarly literature on nuclear fallout and antimalarial DDT pesticide in the United States and Global South, I engage with the geopolitics, historical events, and fundamental actors that shaped the emergence of planetary health. Using ethnographic methods, I also set RF’s promotional language and PHA’s infrastructures in conversation with the current challenges shared by field experts to tease out the paradoxical dimensions of planetary health’s historical entanglements with the RF. These findings are relevant for policymakers, medical experts, and the general public interested in the influence of biomedicine, philanthropic aid, and geopolitics on human and environmental health problems at a global-scale.