The COVID-19 pandemic increased the worldwide prevalence of metabolic syndrome. The purpose of this study was to assess health behavior adherence during the pandemic in adults who had engaged in a metabolic syndrome management program for at least 6 months. This assessment included an evaluation of health behavior changes, factors influencing adherence, and clinical parameters. The city-wide program was operated by the Seoul Metropolitan Government. Baseline and follow-up data were compared in 116 participants who engaged in the program for at least 6 months prior to the pandemic. Health behaviors and clinical parameters were examined. Generalized estimating equation analysis was used to identify sociodemographic variables influencing health behavior adherence over time. Systolic blood pressure, waist circumference, and blood glucose improved (all P<0.05), and risk factors decreased (P<0.001) from baseline to follow-up (mean±standard deviation, 1.13±0.91 years). All six health behaviors, physical activity and weight control, eating habits, alcohol consumption and smoking, stress management, sleep and rest, and medication compliance and medical examination improved (all P<0.001) from baseline to follow-up (2.37±1.05 years). Smoking and employment negatively influenced adherence to health behaviors (P<0.05). Participants felt the most beneficial part of the program was receiving sequential medical examination results with follow-up consultations by public health professionals without charge. Our study demonstrated the durability of the impact of the Seoul Program on all six targeted health behaviors as well as clinical parameters. Findings encourage participation in such broad-based programs and development of novel approaches to facilitate success for smokers and employed participants.