Companies are increasingly committed to pursuing social goals with the development of Social Innovation (SI), but they need to adopt adequate mechanisms to effectively manage, promote and sustain it in the long term. This paper aims to explore how businesses leverage Open Innovation (OI) practices to tackle social challenges in collaboration with SI stakeholders. We performed a multiple case study in three large manufacturing enterprises that are well-known for their excellence in innovation in terms of both SI impacts and OI depth. Results show that businesses develop and nurture a set of SI capabilities founded on purposeful knowledge exchanges across organizational boundaries, enhancing innovativeness, sustaining SI and enlarging SI social and economic outcomes. The study provides key insights into the interplay between OI and SI, still underinvestigated in the literature, identifying the capabilities that should be fostered in the innovation processes of companies tackling broad societal challenges with openness.