The general disproportion of urban development and the socio-economical crisis in Serbia, followed by a number of acute and chronic stressors, as well as years of accumulated trauma, prevented the parallel physical, mental and social adaptation of society as a whole. These trends certainly affected the quality of mental health and well-being, particularly on the vulnerable urban population, increasing the absolute number of people with depression, stress and psychosomatic disorders. This study was pioneering in Serbia and was conducted in collaboration with the Faculty of Forestry, the Institute of Mental Health and the Botanical Garden in Belgrade, in order to understand how spending time and performing horticulture therapy in specially designed urban green environments can improve mental health. The participants were psychiatric patients (n=30), users of the day hospital of the Institute who were randomly selected for the study, and the control group, assessed for depression, anxiety and stress before and after the intervention, using a DASS21 scale. During the intervention period the study group stayed in the Botanical garden and participated in a special programme of horticulture therapy. In order to exclude any possible “special treatment” or “placebo effect”, the control group was included in occupational art therapy while it continued to receive conventional therapy. The test results indicated that nature based therapy had a positive influence on the mental health and well-being of the participants. Furthermore, the difference in the test results of the subscale stress before and after the intervention for the study group was F1.28 = 5.442 and p<;.05. According to socio demographic and clinical variables, the interesting trend was recorded on the subscale of anxiety showing that the male participants in the study group were more anxious, with the most pronounced inflection noted on this scale after treatment. The results of this study have shown that recuperation from stress, depression and anxiety was possible and much more complete when participants were involved in horticulture therapy as a nature-based solution for improving mental health.