Health promotion has struggled to demonstrate its ability to reduce social inequalities in health. This exploratory study uses the realistic evaluation approach to identify, within five initiatives, the mechanisms that contribute to reducing social inequalities in health in France. Case studies were conducted based on five health promotion initiatives in three regions. Data were drawn from 41 individual interviews and documentation of the initiatives. The interviews were conducted to explore a list of 51 candidate mechanisms selected using three tools derived from the literature. Data analysis was performed using content analysis. The following mechanisms were confirmed by this empirical study: involvement of all key partners, meaningful participation, recognition of different types of contributions and knowledge, shared vision, shared leadership, continuous critical reflection on processes and outcomes, and mobilization of resources. This exploratory research confirmed, through empirical data, the existence of these mechanisms specific to actions aimed at reducing social health inequalities from the perspective of the actors involved. At the same time, it identified new candidate mechanisms that warrant further exploration in future research. The analysis shows, however, that one should not focus solely on mechanisms but also broadly consider the role of political entrepreneurs in the success of these initiatives. This exploratory research demonstrates that the realistic evaluation approach is feasible, but it should be replicated on a larger scale to access the full body of knowledge necessary for a more comprehensive understanding of the mechanisms conducive to reducing social inequalities in health in France. [author’s abstract]