This research addresses current debates on the role of social capital in the context of urban shrinkage, by investigating the specific role of informal social capital. The results are drawn from qualitative studies conducted in two French medium-sized shrinking cities. The findings show that similarly to the institutional and collective forms of social capital analyzed in previous literature, informal social capital is also impacted by the changes affecting urban place in the context of shrinkage, and particularly weakened for elderly residents – especially women – and young professionals. At the same time, it constitutes an efficient resource, that helps residents facing shrinkage-related problems individually rather than addressing shrinkage itself collectively. Finally, the findings highlight the role of specific social actors such as community centres who, by providing institutionalized sources of social capital, foster the creation of informal social capital and allow us to address its unequal distribution and weakening. This emphasizes the need to reconsider current social capital-based planning strategies, from relying mainly on collective initiatives addressing shrinkage, to supporting institutional social actors in the creation of small scale, individual level social ties and interactions.