The development of supervisors' behaviours has been proposed as an innovative approach for the reduction of employees' work stress. The UK Health and Safety Executive (HSE) developed the "Stress Management Competency Indicator Tool" (SMCIT), designed to be used within a learning and development intervention. However, its psychometric properties have never been evaluated, and the length of the questionnaire (66 items) limits its practical applicability. We developed a brief 36-item version of the questionnaire, assessed its psychometric properties and studied the relationship with the employees' psychosocial work environment. 353 employees filled in the brief SMCIT and the "Stress Management Indicator Tool". The latter is a self-report questionnaire developed by the UK HSE, measuring workers' perceptions of seven dimensions of the psychosocial work environment that if not properly managed can lead to harm. Data were analysed with structural equation modelling and multiple regressions. The results confirmed the factorial structure of the brief SMCIT questionnaire and mainly supported the convergent validity and internal consistency of the scales. Furthermore, with few exceptions, the relations hypothesized between supervisors' competencies and the psychosocial work environment were confirmed, supporting the criterion validity of the revised questionnaire and the UK HSE framework. We conclude that the brief 36-item version of the SMCIT represents an important step toward the development of interventions directed at supervisors and we discuss the practical implications for work stress prevention.