In this article, we explore longitudinal video data from the student activist group Fossil Free UofT to analyze what it means to become politicized. We argue that politicization is a sociocultural learning process, not merely a process of conceptual development or cognitive change, but a simultaneous process of conceptual, practical, epistemological, and identity development. In the analytic sections, we tease apart aspects of politicization, showcasing examples of transformation that center political concept development, changing practices, reconfigured ways of knowing, and new identities in formation.