We describe 7 cases of splenic smooth muscle tumors in dogs. Histopathological and immunohistochemical analysis revealed that 6 cases were diagnosed as splenic leiomyosarcoma and 1 case as leiomyoma. All dogs underwent splenectomy without chemotherapy, and one of them was euthanized 2 months after surgery because of hepatic metastasis. Of the remaining 6 dogs, 5 died in the postoperative period and only one dog survived > 4 years. The median survival of the 6 dogs was 16.9 months. To the best of our knowledge, this is the first detailed study on splenic smooth muscle tumors in dogs in Korea.