A 14-year-old, mixed breed bitch was presented for investigation of progressive abdominal distension, dyspnea and general dullness. A large abdominal mass including numerous cystic areas was visualized in abdominal radiologic examinations. Moreover, some abdominal organs were displaced from their abdominal anatomical locations. Exploratory laparotomy revealed a uterine mass, which was removed by ovariohysterectomy. Histopathology confirmed uterine leiomyosarcoma. Clinical and radiographic examination did not reveal any evidence of metastasis two months after surgery. Canine uterine leiomyosarcomas are rare tumours, grow slowly and are not regarded as highly metastatic. In this case, removal of this huge tumor by ovariohysterectomy following laparotomy was successful as metastasis did not subsequently occur.