Background: The best investment is to have good health. One way to have good health is to adopt a healthy lifestyle, especially physical activity. As an investment, start a healthy lifestyle earlier; the better the health. Many factors influence teenagers in doing regular physical activity. This study examined the teenagers' barriers, beliefs, and the degree of desire to adopt good physical activity behavior. Methods: A cross-sectional online survey was completed by 19 males and 40 female teenagers aged 17 to 18 in Purwokerto, Indonesia. Result: Results identified that 61.02% of teenagers did not have regular physical activities. The common barriers to exercise were lack of energy (94.92%), lack of will (88.14%), lack of resources (76.27), lack of time (69.49), lack of skill, and lack of social support (66.10%). A total of 81.36% of teenagers believe they can do physical activity regularly. The degree of the desire of teenagers to adopt good physical activity behavior was 79.66% had high, and 20.34% had a moderate degree. Conclusion: This study concluded that most adolescents believe they are capable and have a strong desire to do physical activity regularly, but managing it has many obstacles. Findings suggest that health promotion could engage teenagers in improving physical activity behaviors by reducing barriers, such as time management, benefit, increasing energy and fitness, and building social support related to physical activity.