We report a case of a huge gastric gastrointestinal stromal tumor(GIST)that was safely resected followingpreoperative imatinib therapy. A 72-year-old woman was hospitalized with severe abdominal distension. Computed tomography revealed a 27×17 cm tumor in the left upper abdominal cavity. The patient was diagnosed with high risk GIST by EUS-FNA. We initiated preoperative adjuvant chemotherapy with imatinib to achieve a reduction of operative risks and functional preservation. After 6 months of chemotherapy, CT showed a reduction in the tumor size and the patient underwent partial gastrectomy and partial resection of the diaphragm. Histologically, most of the tumor cells were replaced by hyalinized collagen and viable cells were scattered only around the blood vessels. Neoadjuvant chemotherapy with imatinib has the potential to become an important therapeutic option for the treatment of huge GISTs.