The small bowel is the least common site for cancer to arise. Only approximately 1% of all gastrointestinal neoplasms arise in the small bowel. Mucinous adenocarcinoma is diagnosed when the amount of extracellular mucin in a tumor is over 50%. Because it is a very rare disease, there is little data available concerning its incidence, most common site of origin, and common sites of metastasis. There are no case reports describing primary mucinous adenocarcinoma of the jejunum in Korea. We report a case of jejunal mucinous adenocarcinoma metastatic to the stomach presenting as a submucosal tumor. (Korean J Gastrointest Endosc 2008;37:192-197)