Climate change and sustainability science have become more international in scope and transdisciplinary in nature, in response to growing expectations that scientific knowledge directly informs collective action and transformation. In this article, we move past idealized models of the science–policy interface to examine the social processes and geopolitical dynamics of knowledge mobilization. We argue that sociotechnical imaginaries of transdisciplinary research, deployed in parallel to “universal” regimes of evidence-based decision-making from the global North, conceal how international collaborations of scientists and societal actors actually experience knowledge mobilization, its systemic barriers, and its paths to policy action. Through ethnographic study of a transdisciplinary research program in the Americas, coupled with in-depth analysis of Colombia, we reveal divergences in how participants envision and experience knowledge mobilization and identify persistent disparities that diminish the capacity of researchers to influence decision-making and fit climate knowledge within broader neoliberal development paradigms. Results of the study point to a plurality of science–policy interface(s), each shaped by national sociotechnical imaginaries, development priorities, and local social orders. We conclude that a geopolitical approach to transdisciplinary science is necessary to understand how climate and sustainability knowledge circulates unevenly in a world marked by persistent inequality and dominance.