Leiomyosarcoma is an uncommon tumor that originates from various organs, including uterus, kidney, retroperitoneum, and soft tissues. In particular, leiomyosarcoma of the stomach is extremely rare. Only 9 cases have been reported worldwide since the discovery of KIT-activating mutation. A 48-year-old woman was admitted to our hospital with abdominal discomfort and generalized weakness. Upon detection of multiple nodules in both lung on chest posterior-anterior radiograph taken at the time of admission, chest CT was performed and it revealed multiple mass lesions in the lung, liver, and pancreas along with multiple lymph node metastases. On endoscopic examination, a 2.0 cm sized ulcerofungating mass lesion was found on the stomach body. Biopsy was performed and the mass lesion proved to be leiomyosarcoma confirmed by immunohistochemical staining. Chemotherapy was thus initiated, but the patient died after one year due to tumor progression. Our experience suggests that leiomyosarcoma can manifest aggressive behavior in its early stage. Herein, we report a case of gastric leiomyosarcoma with multiple metastases along with review of relevant literature.