The present study evaluates the effectiveness of a supervisor support training programme on both supervisor attitudes and employee sleep and stress outcomes by drawing on a multi-level rigorous randomized controlled trial in 35 organizations. Utilizing theory from the social support and training literatures, the purpose of the current study was to understand ways to improve the transition, and ultimately the health and well-being, of military veteran employees in the workplace via a supervisor support training intervention. Drawing on a sample of 982 supervisors and a subsample of 189 matched supervisor–employee dyads, the current study demonstrated that supervisor support training led to improved supervisor attitudes towards veteran employees. Additionally, supervisors’ attitudes towards veteran employees at baseline significantly moderated the effects of the training on employee sleep and stress outcomes, suggesting that the training was more effective when supervisors started out with more positive attitudes towards veterans. These results demonstrate the importance of training supervisors to support employed veterans and employees more generally, and have implications for research, practice, and theory development.
Practitioner points:

• The Veteran Supportive Supervisor Training (VSST) promotes more positive supervisor attitudes towards veteran employees.
• When supervisor attitudes towards veteran employees are more positive, the supportive supervisor training improves sleep and stress outcomes for veteran employees.
• The VSST effects suggest that the training has promise to be extended to other leadership support domains, such as supervisor support for health; to other types of vulnerable and underserved workers, such as those with disabilities; and to other employee well-being outcomes, such as engagement and satisfaction at work and at home.