Objective: Little is known about the effects of psychodrama group therapy on the level of stress, anxiety and depression of the group members, and the biological markers of stress. The aim of this study test cortisol level as a biological reflection of some mental characteristics gained by the psychodrama method in coping with stress. Methods: Depressive patients aged between 18 and 65 years, who diagnosed with depression according to DSM-5, without psychiatric comorbidity, who do not use drugs and were available for psychodrama were enrolled into the study. These patients were evaluated using the Perceived Stress Scale, State-Trait Anxiety Inventory and Beck Depression Inventory. In order to observe the circadian rhythm of cortisol, samples were collected from the participants before lunch, before dinner and before going to sleep on the day before psychodrama and on the 0, 15th, and 30th minutes after awakening in the morning of the psychodrama day; as well as just before and after the psychodrama session. Saliva cortisol level just before the initial session of psychodrama group therapy was compared with the saliva cortisol level just after the last psychodrama session at the end of 16 weeks. Results: Statistically significant difference was determined between the scores of perceived stress scale, STAI-1, STAI-2, beck depression inventory and salivary cortisol level before and after psychodrama session. There was significant decrease in both the scale scores and salivary cortisol after vs. before psychodrama. Conclusion: This results is important as it shows the biological aspect of clinical improvement. Further studies would provide us with better understanding of the effects of psychodrama group psychotherapy on depressive mood and biological projections by means of short-term and long-term follow-up studies.