Business schools increasingly need to demonstrate the societal impact of their activities to a broad range of stakeholders, both internal and external. With societal impact being a hard-to-measure performance dimension, business school deans find it challenging to create societal impact governance processes that reconcile multiple legitimate perceptions of what societal impact is. The result is that individual-level societal impacts (influences on society attributed to individual employees) are not aggregated into organizational-level societal impact (influence attributed to an organization) in ways that are effective and legitimate. In this paper, we develop a model that provides insights into the process of legitimation for societal impact governance at the organizational level. We address the emergence of different types of legitimacy and the sequencing of legitimation stages that reduces internal decoupling and increases the perception of procedural justice. In a practical sense, our model helps in designing a decision-making process that addresses what societal impact is, how to measure it, and how much should be spent on its measurement. We develop and share a set of tools and frameworks that can be used to support the legitimation of societal impact evaluation and governance.