The platform governance literature has implicitly recognized the role platform actor coordination and monitoring plays in shaping platform culture (i.e., the cultural values, norms and practices espoused by platform actors). But the lack of explicit scholarly attention to platform culture has left many unanswered questions about how, why, and when platform governance may foster different platform cultures. We begin to address these questions by first developing a conceptual governance framework based on two generalizable culture-shaping levers: the nature of incentives and rewards emphasized by platform owners (transactional vs. socioemotional), and the way in which platform owners make them available to platform actors (generalized vs. targeted). The interactions of these levers inform our theorizing of four distinct platform cultures: commercial autonomy, commercial discipline, communal affiliation, and communal kinship. We also identify key conditions that exist ab initio that either reduce, or increase risk in actors’ value exchange, and ultimately motivate the diffusion of different cultural values, norms, and practices on platforms. Our work proposes a parsimonious model as a springboard for many theoretical and methodological extensions, which we also discuss. We conclude with our contributions to the research on platform governance and platform design.