Hemoperitoneum is a common cause of emergency surgery. Common gynecologic causes of hemoperitoneum include ruptured ectopic pregnancies, bleeding ovarian cysts, and very rarely, bleeding from uterine masses secondary to infarction and ulceration or ruptured superficial veins, secondary to increased intra-abdominal pressure. However, spontaneous bleeding of a uterine mass without any history of trauma, increased abdominal pressure, recent pregnancy, or menstruation is very rare. Herein the authors report two cases of acute abdomen secondary to spontaneous bleeding of a ruptured uterine smooth muscle tumor of unknown malignancy potential and endometrial stromal sarcoma. In the differential diagnosis of hemoperitoneum, uterine tumors should be considered as a potential site of the bleeding.