Research in ergonomics and work psychology has been interested in the way to prevent musculo-skeletal and psycho-social risks in companies for many years. Globalization of an efficient approach is not easy to find. This is why research turns towards understanding the social construction of a preventive approach with workers. It would be necessary to have workers take an active part in the deployment of a preventive approach to make its effects lasting (Coutarel α Daniellou, 2007). In this way, the concept of the mobilization of stakeholders is being used more and more. Mobilization of stakeholders during a prevention process is a fundamental condition for the efficacy of an intervention. The aim of this paper is to show the conditions favoring the mobilization of stakeholders in a preventive approach. To understand this issue, we explore three hypotheses: the influence of the practitioner in the mobilization process (hypothesis 1), the role of the individual activity of each worker (hypothesis 2) and the construction of collective work (hypothesis 3). The contribution of this article is to improve intervention practices by encouraging the diagnoses and actions that must be carried out to facilitate the stakeholders‘ mobilization, which is an important issue for the efficacy of prevention.