Uterine inversion is a rare complication of the postpartum period, but it is an even rarer complication of the non-puerperal period. A 49-year-old nulliparous woman was admitted to the hospital with the following complaints: abnormal vaginal bleeding, pain, anuria and a mass protruding from the vulva. The mass was removed by twisting and a laparotomy was required for massive bleeding due to the inversion. The diagnosis of complete inversion was made during the laparotomy. Total abdominal hysterectomy and bilateral salpingo-oophorectomy was performed and the pathological examination revealed a leiomyosarcoma. Uterine inversion in the non-puerperal period is an extremely rare event and it should be kept in mind that the cause of the inversion may be a malignant disease, like leiomyosarcoma.