This chapter explores the interrelation between social entrepreneurship and social capital at the neighbourhood level. Although the relevance of social capital theory for explaining the phenomenon of social entrepreneurship is obvious and undisputed, in-depth academic studies in this area remain scarce. We link social cohesion and collective efficacy, two neighbourhood-level components of social capital, to social entrepreneurial activity in the neighbourhood. In this way, we connect the theoretical perspectives of ‘institutional void’ and ‘institutional support’ that are addressed in the social entrepreneurship literature. We investigate these relations by using a sample of 360 entrepreneurs in 161 Dutch neighbourhoods and their report of the values they attach to societal and economic goals in their businesses. We find that in particular, collective efficacy in neighbourhoods can be linked to social entrepreneurship. This effect appears to be non-linear and U-shaped, which supports the idea that both a lack (signalling ‘institutional void’) and an abundance (signalling ‘institutional support’) of collective efficacy may trigger social entrepreneurial activities in a neighbourhood.