This paper presents the findings of our EU co-funded project, an idea developed to better understand the opportunities to formalize corporate social responsibility (CSR) practices for small and medium enterprises (SMEs) in a clustered system. Small companies often have to compete in a global market; for this reason, cooperation among SMEs, and with local stakeholders and intermediary institutions, might be facilitated by a collective answer to new market requests. Cooperation and social capital are key elements to facilitate trust amongst involved local actors. Moreover, they can also play a key role in the formalization of CSR policies and practices for small companies. In our project, we aimed at identifying and understanding the role of the ‘intermediary institutions’ (such as trade unions, local authorities, business consortia) in the cluster. Throughout the paper, we focus on the analysis of three industrial clusters in Tuscany (Italy).