This field study evaluates the process and outcome of an organizational-level stress management intervention (SMI) in eight companies, taking into account the lessons learned from previous evaluation research. It utilizes the RE-AIM evaluation framework to capture the Reach and Adoption of the intervention in the companies, the appraisal of the Implementation process and the project's Effectiveness and Maintenance with a range of qualitative and quantitative methods. It applies an adapted research design in the context of a field study involving entire organizations, retrospectively assigning study participants to comparison groups. The results of a longitudinal analysis (n = 1400) showed that the SMI had a positive impact on the participants' job demands and resources, when controlled for baseline levels. Qualitative data analysis revealed that the companies had built capacities for ongoing health promotion and showed what issues must be borne in mind when implementing such projects. The study also showed that participation in such interventions alone does not suffice to achieve the desired impact, but that the individual participants' appraisal of the intervention and the collective involvement of the teams must be further researched to fully understand how change occurs.