Background: Aging is a sensitive period of human life and, considering the special needs and the behaviors that lead to mental health promotion and quality of life, this period is very important. The useful methods used to maintain mental health, reduce stress and make one more adaptive are doing physical activities and aerobic exercises. No studies in the past have investigated variety of exercises such as the role of hiking on mental health and happiness of elderly women. Objectives: This study was done to evaluate the impact of the six-week hiking on happiness and mental health of elderly residing in Semnan. Patients and Methods: Twenty-seven elderly women with a mean age of 61 years were randomly selected in two groups with available sampling; the case group with 14 participants and the control group with 13. The case group took part in walking exercises. Both groups completed the Persian Version of the oxford happiness inventory (OHI) before and after exercises. This inventory contains 29 items, which evaluates happiness components; self-esteem, positive mood, life satisfaction, efficiency and mental health. Results: There was a significant difference in the self-esteem (P = 0.003), life satisfaction (P = 0.001), efficiency (P = 0.00), positive mood (P = 0.00), mental health (P = 0.001) and happiness (P = 0.001) among elderly women in the case group before and after a regular six-week walking program. Conclusions: According to the results, walking increases the happiness and mental health of elderly women. Therefore, promoting the habit of walking as a public activity among elder women could have a significant impact on them.