The difficulties associated with the evaluation of organizational-level work stress interventions are notorious yet little attention has been paid to the reasons why they fail. This case study took place in a department of 205 employees from a private company where an intervention was developed but poorly implemented. This paper scrutinizes the intervention to understand why it was poorly implemented and examine its effects on employees. Qualitative data (field notes and interviews with managers) was used to evaluate the intervention. Questionnaires (n = 125, n = 94, 60 full-completers) were used to evaluate the level of implementation and its effects. Results suggest partial implementation might have a detrimental effect on commitment. Poor implementation could be accounted for by the changing organizational context, low ownership of stakeholders, and flaws in the intervention design. Considering the process and context of interventions is essential to understand their effects