Introduction: Despite its efficacy, conventional center-based cardiac rehabilitation has several limitations which have led to the emergence of home-based programs and intensive cardiac rehabilitation as alternative methods for overcoming these limitations. Alternative methods for primary prevention have been recommended for similar reasons. Lifestyle modification is considered key to success in both primary and secondary prevention. Therefore, this primary prevention study aimed to investigate the efficiency of intensive lifestyle education and home-based programs involving unstructured exercise in urban forests to prevent coronary artery disease (CAD). The availability of urban forests as preventive exercise environments was also examined. Methods: Patients with risk factors for CAD participated in primary prevention using either FBEG (forest-based exercise group (FBEG, n = 11) or CBEG (center-based exercise group (CBEG, n = 17) for 12 weeks. The FBEG was provided with intensive residential lifestyle education and followed a home program that included performing exercise in an urban forest. The CBEG followed a conventional supervised exercise program at a fitness facility. Changes in body composition, cardiometabolic variables, and functional capacity were tested using a 2-way repeated ANOVA measurement. An independent t-test was used to examine the differences in weekly energy expenditure between the two groups. Results: Significant within-group differences were identified in body composition, cardiometabolic variables, and the 10-yr probability of CAD in both groups. However, the functional capacity, weekly energy expenditure, and attendance rate showed between-group differences, with superiority in the FBEG. Conclusion: Intensive lifestyle education and subsequent home-based programs with unstructured exercise in the forest were as effective as a conventional center-based program, with superiority in terms of the change of some variables. Intensive education on experiencing and habituating a healthy lifestyle seemed to play an important role in improving motivation.