Serious mental illness places a tremendous burden on clients, their families, and behavioral and medical health care providers. The co-occurrence of diabetes with mental illness may further compromise daily functioning. Psychiatric nurses can make a significant difference in improving the health and medical outcomes of this client population. A partnership was developed between the University of Rochester School of Nursing and the Western New York Care Coordination Program to evaluate a novel nursing model for adults with both serious mental illness and diabetes mellitus. The Well Balanced program incorporated health promotion, disease management, nursing care management, and evidence-based practice guidelines into 8 Steps to Wellness for a community-based mental health population. During a 16-visit intervention period, psychiatric nurses interacted with 74 clients. As a result of the program, clients experienced improvements in health risk status and in their hemoglobin A1C and reported high satisfaction with the Well Balanced program.