This study investigates the determinants of exercise adherence among middle-aged adults in Vietnam, focusing on the roles of health motivation, social support, exercise self-efficacy, and digital health technology use. A quantitative research approach was employed, and data were collected from 487 middle-aged adults aged 40 to 60 years through a structured questionnaire. The proposed model was analyzed using SPSS 26.0 and SmartPLS 4.0. The results revealed that all four factors significantly and positively influence exercise adherence. Exercise self-efficacy was identified as the strongest predictor, followed by health motivation, digital health technology use, and social support. The findings indicate that individuals who possess greater confidence in their ability to exercise, stronger health-related motivation, higher levels of social support, and more frequent use of digital health technologies are more likely to maintain long-term participation in physical activity. The proposed model explained 61.2% of the variance in exercise adherence. These findings provide important implications for health promotion programs, fitness organizations, and policymakers seeking to encourage active lifestyles and healthy aging among middle-aged adults in Vietnam.