In 1996 the NewYork State Office of Mental Health issued a policy requiring all State-operated psychiatric facilities to develop and implement a proactive violence-prevention program based on guidelines issued by the US Occupational Safety and Health Administration. This presented an opportunity to evaluate the impact of the guidelines on worker health and safety. The authors report the findings of a mixed-method study to evaluate the feasibility and impact of a participatory intervention to prevent workplace violence. They describe the implementation of the intervention in 3 in-patient facilities, including an extensive worksite analysis, staff focus groups, and a baseline and post-intervention survey of changes in staff perception of the quality of the program's elements and physical assault following implementation of the program. The authors provide evidence for the feasibility and positive impact of a comprehensive violence-prevention program in the in-patient mental health workplace. Staff perception of the quality of management commitment and employee involvement in violence-prevention was significantly improved in all worksites post-implementation.