Abstract: Menopause is associated with complications that could decline women's health during this period. Therefore, some of its complications, such as hot flashes and night sweats, must be treated or alleviated. This randomized controlled trial included postmenopausal women who were referred to health centers in Hamadan from May 2018 to April 2019. The hot flash and night sweat questionnaires were completed by the researcher a week before and 8 weeks after the intervention. The intervention group took one capsule (1,000 mg) of evening primrose oil twice daily, while the control group received the same amount of placebo. Finally, the results were analyzed using Stata 13. The mean scores of duration, frequency, and severity of hot flashes did not significantly decrease in both groups after the intervention compared with before the intervention, and no statistically significant difference was observed (P > 0.05). However, the intervention group had lower frequency and severity of night sweats after the intervention than the control group, with statistically significant differences (P < 0.05). Evening primrose oil effectively decreased the frequency and severity of night sweats.