Social impact assessment can greatly contribute to sustainable regional and urban planning. However, social impact assessment is used primarily in the context of pre determined projects, while social impact assessment’s role in informing regional and urban plans before projects are even conceived is under-estimated. Moreover, a narrow understanding of the social impacts of projects leads social impact assessment practitioners to consider such impacts as being the outcomes only of the technical characteristics and risks of projects and their implementation, rather than also of broader social, cultural and political-institutional processes. In this article, we reflect on these gaps in social impact assessment. We expand the conceptualization of the social impacts of projects to better consider how social impacts are also influenced by the social dimensions of risk and resilience, and by the knowledge processes and governance strategies that inform and regulate projects. We conceptualize these processes and strategies and design new conceptual models to derive the social impacts of projects. Finally, we reflect on the strategic role social impact assessment can have in enabling social learning and sustainability transformation in localities (i.e. community resilience) and across multiple governance levels (i.e. social resilience). With this article, we contribute to building a key role for social impact assessment in disaster risk reduction, climate action and sustainable development.