This randomized control trial examined the effects of the Self-management Support Program for People with Metabolic Syndrome on eating behaviors, physical activity, and metabolic control in three hospitals in Northern Thailand. Eighty-six participants who met the inclusion criteria were randomly assigned to either an experimental (n=44) or control (n=42) group. The experimental group received a self-management support program based on the self-management 5A model by Glasgow and colleagues, while the control group received standard care. The program duration was three months, and included six sessions; once a week for the first four weeks, then monthly for the second and third months. The sessions covered one education (diet and physical activity) session, three self-management skill training sessions, and two discussion sessions. Data was collected at baseline, three and six months. Eating behaviors were assessed using the Seven-Day Food Diary, while data on physical activity was collected using the Physical Activity Log. Data pertaining to metabolic control, waist circumference, systolic and diastolic blood pressure, blood glucose, triglycerides and HDL cholesterol was also collected. The findings showed a significant positive effect on physical activity at 3-months and 6-months, and significant improvement in metabolic control including blood glucose and HDL cholesterol only at 6-months. However, this Program could not significantly improve eating behaviors, waist circumference, systolic and diastolic blood pressures, or triglyceride levels. Nurses may implement this Program to achieve designated outcomes, especially for controlling blood glucose and HDL cholesterol as well as determining barriers to change behaviors in targeted patients.