This study aimed to assess the effectiveness of emotion regulation training in reducing pain catastrophizing, negative emotion, and pain intensity in women with dysmenorrhea. The research employed a quasi-experimental design with pretest-posttest and a control group. The statistical population included all women with dysmenorrhea in Tehran in 2020. From this group, 30 participants were purposefully selected based on inclusion criteria and randomly assigned to experimental (15) and control (15) groups. Data were collected using the Pain Catastrophizing Scale, Chronic Pain Intensity Questionnaire, and Negative emotion Questionnaire. Results from univariate and multivariate covariance revealed that emotion regulation training significantly reduced pain catastrophizing (rumination, magnification, and helplessness), negative emotion, and pain intensity in the experimental group.