Objective: This study aimed to identify factors affecting the severity of dysmenorrhea in women attending outpatient gynecologic clinics. Methods: A total of 160 premenopausal women who visited outpatient gynecologic clinics at Seoul National University Bundang Hospital between January 2017 and July 2018 were retrospectively evaluated. Data on age, height, body weight, marital status, parity, amount of menstrual bleeding (assessed by pictorial blood assessment chart), and severity of dysmenorrhea (assessed by visual analog scale) were collected from electronic medical records. Results: Of the premenopausal women enrolled, 99, 33, 10, and 1 had uterine myomas, uterine adenomyosis, endometriosis, and endometrial polyp, respectively. The severity of dysmenorrhea was positively associated with the amount of menstrual bleeding (r = 0.192, p = 0.015), but was negatively associated with age (r = -0.198, p = 0.012) and parity (r = -0.244, p = 0.002). In multiple regression analysis, the amount of menstrual bleeding (B = 0.003, p = 0.025) and parity (B = -0.652, p = 0.028) were significant factors for the severity of dysmenorrhea. The positive association between the severity of dysmenorrhea and the amount of menstrual bleeding was noted in women with uterine adenomyosis (B = -0.218, p = 0.032) but not in women with uterine myomas. Conclusion: We observed that the severity of dysmenorrhea is closely associated with the amount of menstrual bleeding and parity. The positive association between the severity of dysmenorrhea and the amount of menstrual bleeding was prominently noted in women with uterine adenomyosis.