This study was conducted in a Tunisian context with the aim of understanding the role that the union and the works council can play in the process of Corporate Social Responsibility (CSR). Three companies were studied by means of an interpretive epistemological approach and qualitative methodology. To carry out this comprehensive research, data were collected from three sources : field notes ; semi-structured interviews ; and the company’s CSR reports. The main results show differences from one case to another in (1) CSR types, (2) CSR commitment reasons and (3) types of regulation. The type of regulation depended on the rule governing the mode of CSR practice and management. The results allow us to conclude that, in all cases, the union and the works council are an essential stakeholder in CSR through their mobilizing capacity and the various types of regulation that strengthen or weaken the CSR process. Social dialogue appears as a powerful lever to legitimize and develop CSR practices through joint collective action. As a CSR tool that is both robust and pragmatic, social dialogue regulates the process and reifies the actor’s aspirations around this construct (CSR).