This study aimed to investigate the effects of mindfulness-based mandala coloring made within nature on individuals with chronic widespread musculoskeletal pain (CWP). Thirty-six participants were randomly allocated. In the experimental group, identical interventions and procedures were administered for each experiment. The control group members were untreated and remained in an urban environment. Overall, the experiment showed significant improvements in tender points (f = 8.791, p = 0.006), total stress level (f = 14.570, p = 0.001), depressive symptoms (f = 15.205, p = 0.001), anger symptoms (f = 7.263, p = 0.011) and salivary cortisol (f = 10.619, p = 0.003) in the experimental group. The results reflect that MBMC within nature is effective in reducing pain, psychological stress responses, and cortisol levels in individuals with CWP. The positive results could be a product of the experimental design rather than the treatment itself. A rigorous experimental design provides better understanding of MBMC within nature.