Endometriosis is defined as the growth of endometrial tissue outside the uterine cavity and its occurrence is usually related anatomically to the uterus and its attachments. Cutaneous endometriosis occurs most commonly as a secondary process in scars after abdominal or pelvic procedures including hysterotomy, hysterectomy, cesarean section, episiotomy, and laparoscopy. Because of the rarity of cutaneous endometriosis, and the failure of the recognition of the correlation between the intensity of the pain and the menstrual cycle, the diagnosis can be easily missed. We present a case of cutaneous endometriosis occurred in the scar of a previous cesarean section in a 27-year-old woman.