Background: The benefits of walking in natural environments for well-being are increasingly understood. However, less well known are the impacts different types of natural environments have on psychological well-being. Aim: The purpose of this study was to determine the effect of green walking on psychological wellbeing of middle-aged women in women park. Methods: The statistical population is 40 women of 48-59 years old, which has gone to one of the health houses of the second district of Tehran for group consultation. Among them, 30 women who had the lowest psychological wellbeing score was chosen as the original samples and were placed randomly into two groups of experimental (15) and control (15). The intervention program was the eighth session of walking in women park of Tehran. Psychological wellbeing questionnaire was implemented in both control and experimental groups, before the first session and after the last session of the hike. Results: The results of ANCOVA test analysis showed a significant difference between psychological wellbeing of experimental group and control group. Also, the study demonstrated that green walking program had positive effects on increasing the personal growth, positive relations with others, self-acceptance, and purpose in life, but it has no meaningful effect on Environmental mastery. Conclusions: Overall, the present results indicate that a green walking in the parks and green spaces because of good weather conditions, less noise and enhance social relationships can be reduces mental stress, and the middle-aged women feel mirthfulness, happiness and well-being.