Brunner's gland hamartomas are rare tumors of duodenum, they are often discovered incidentally during esophagogastroduodenoscopy or upper gastrointestinal series. These tumors arise mainly in the duodenal bulb and can present with gastrointestinal hemorrhage and intestinal obstruction. Most of Brunner's gland hamartomas are located within the range of the standard esophagogastroduodenoscope. However, they are rarely located below the third portion of duodenum. As well known, the small intestine, including the 4th portion of duodenum, jejunum, and ileum, is relatively inaccessible with routine endoscopy. Thus, the diagnosis of Brunner's gland hamartoma in these area can be delayed up to several months after onset of symptoms. We report a case of Brunner's gland hamartoma which was located in the fourth portion of the duodenum and presented as obscure gastrointestinal hemorrhage. Radiologic, surgical, and pathologic appearances are presented.