Social innovation (SI) impacts are long-term changes that affect different dimensions of territorial capital (i.e., economy, society, environment, governance) for the territory in which SI occurs. Yet, systematic empirical evidence and theoretically sound assessments of the impacts of SI are scarce. This paper aims to fill the gap and assess the different aspects of SI’s impacts in European and Mediterranean areas that are characterized by marginalization processes. To assess the impacts of SI in marginalized areas, we use the evaluation framework developed within the Social Innovation in Marginalized Rural Areas (SIMRA) Horizon 2020 project and apply it to nine SI initiatives related to the fields of agriculture, fisheries, forestry, and rural development. Our findings show that SI produces cross-sectoral (societal, economic, environmental, and governmental) and multi-level impacts (on individuals, community, and society), which have improved the societal well-being, and contributed to the reduction of certain forms of marginality, mainly inside the territory in which SI occurred.