Summary There is increasing scientific evidence that psychosocial risk (PSR) factors, such as high psychological demands, low decisional latitude, weak social support and an imbalance between effort and recognition received at work contribute to the development of mental health problems, musculoskeletal disorders, and cardiovascular disease. These health problems are among the main causes of absence from work due to illness. The literature on preventive actions regarding mental health focuses mainly on measures to change certain individual characteristics (such as workers’ lifestyles), instead of organizational characteristics (for example, employment conditions and organization). Organizational interventions are complex and include multiple activities that simultaneously affect many psychosocial risk factors. Although a number of studies have shown that such measures can effectively improve mental health in the workplace, very few of them have attempted to delve into the factors that may help or hinder their implementation. Managers play a key role in the establishment of preventive measures in the workplace. In that context, the general objective of this study is to identify the conditions that facilitate or limit the adoption of preventive approaches to mental health in the workplace by managers. More specifically, the study aims to document the existing approaches to mental health at work. provide managers with tools to deal with psychosocial risks (e.g., guides, examples of best practices) that will support the approach aimed at improving mental health in their organization. discover which factors help or hinder (a) organizational measures to improve mental health; (b) the adoption of management practices to further good mental health. Four organizations engaged in a prevention process in terms of mental health in the workplace participated in this longitudinal study, and 73 managers attended the information session on tools to manage psychosocial risks. A mixed methods research design was used. To document the factors helping or hindering the adoption of organizational approaches to mental health, individual interviews (N = 25) with managers and key stakeholders were carried out. To assess the factors influencing managers’ adoption of management practices to further good mental health, two measurements by questionnaire were administered at three-month intervals (N = 144 in period 1; N = 166 in period 2, N = 118 during both periods). In terms of factors helping or hindering organizational approaches to mental health, the individual interviews highlighted those related to the context, the process and the content of the interventions. With respect to organizational context, management commitment to the approach is the helping factor most often reported by the participants. The integration of the approach into strategic planning and a good communication strategy to promote it are also considered as helpful factors. On the other hand, the geographical distances separating workers, strained relationships among stakeholders engaged in the process and the complexity of the approach are hindering factors. With respect to the process, internal (human resources and inter-site committee) and external (a range of specialized sources) resources are considered to be critical in assisting the organization with a preventive approach. Their expertise is especially necessary given the complexity of the approach, and, sometimes, its lack of adoption, which the participants themselves point out. The commitment of the stakeholders (i.e., the managers, employees and unions) appears to be an important factor in helping the approach, in addition to the need to choose a resource person for it. Finally, in terms of the content, the relevance and value of the activities implemented are sometimes questioned. The principal obstacle found in terms of adoption of content concerns the lack of tools provided to managers so that they can act. Those managers who had completed one or both measurements by questionnaire indicated the elements that could help them adopt management practices that would support good health. The needs most frequently mentioned are training and coaching, social support (such as a program to help managers and co-development groups), and human resources (in particular, access to an external consultant). The information session on PSR management tools offered by the researchers to 73 managers was aimed at highlighting opportunities for intervention. After the session, 63% of the managers adopted new PSR management practices, generally related to communication, training and recognition. Among those who adopted a new PSR management practice, 85.7% noted positive repercussions in their teams, but 34.5% experienced difficulties in implementing this new practice. In addition to these new practices, the managers who filled out the questionnaires were surveyed about their regular management practices to foster mental health. The managers who adopt more management practices conducive to good mental health perceive that their organization makes mental health a high priority; they have more decisional latitude; they have better relationships with their subordinates; they experience less psychological distress; men and older managers have a greater tendency to adopt management practices that further their employees’ mental health. On a theoretical level, this study contributes to advancing knowledge about models that assess organizational actions to prevent mental health problems in the workplace. This recent field of research is growing and the study gives us a better understanding of how these actions can be implemented by managers. On a practical level, in addition to its review of 25 PSR management tools, the study identifies factors that help or hinder interventions by managers, which, in some cases, helps them adjust the process to prevent pitfalls at an earlier stage.