|The length of small intestine is about 75% of total gastro-intestinal tract, but the incidence of malignacy is account for 2% of it. Whereas most of small intestinal malignancy is duodenal cancer, and the most common histologic type is adenocarcinoma. Duodenal small cell carcinoma is extremely rare. We had a case of a 66-year-old female who visited the hospital to evaluation for RUQ discomfort. Endoscopy was done and large ulcerative lesion is founded at duodenum. The histologic finding was small cell carcinoma. We performed Abdomen-pelvis CT and bladder wall thickening was seen. For confirm the lesion, cystoscopic biopsy of bladder wall was done and pathologic finding was small cell carcinoma, too. In positron emission tomography-computed tomography (PET-CT), we can find multiple metastasis to duodenum, bladder, lung and brain. Finally we diagnosed duodenal small cell carcinoma with multiple metastasis. After 4-cycles of chemotherpy, Irinotecan and Cisplatin, the mass size was markly decreased. However she was expired due to unknown origin infection. We present a extremly rare case of duodenal small cell caricnoma with bladder wall, lung and brain.