The interest in mindfulness meditation interventions has surged due to their beneficial effects in fostering resilience and reducing stress in both clinical and non-clinical populations. However, the relaxation benefits that may occur while practicing mindfulness meditation and long-term benefits of these interventions remain unclear. Fifty-one participants were recruited and randomized into the experimental and control groups, which underwent 4 days of Intensive Meditation (Templestay program, n = 33) and Relaxation (Control, n = 18), respectively. The self-report measures of Cognitive and Affective Mindfulness Scale-Revised (CAMS) and the modified Korean version of the Resilience Quotient Test (RQT) were administered pre-, post- and 3 months after the intervention to measure participants' levels of mindfulness and resilience. Participants in both the Templestay program and Control groups showed significant increases in their scores on CAMS and RQT after completing the program. During the 3-month follow-up, a significant interaction effect of the intervention method and time was revealed for the individuals' CAMS and RQT scores. Our findings support the hypothesis that while relaxation practices may have certain stress reduction effects, the effects are predominantly mediated by the mindfulness meditation practice. Furthermore, the long-term benefits of increased resilience observed in the Templestay program group suggest that the practice may be a possible treatment strategy in clinical populations, such as patients with depression and anxiety.