Although prostate carcinoma is the most common malignancy in males, it rarely involves the gastrointestinal (GI) tract. We report the first case of endoscopically diagnosed prostate carcinoma metastatic to the stomach in an 88-year-old man whose heralding symptoms were nausea, vomiting, and epigastric pain. The initial diagnosis was not suggested at presentation, but an upper endoscopy and biopsy suggested adenocarcinoma of uncertain primary site subsequently confirmed to be of prostatic origin by immunohistochemical staining. We review the clinical aspects and endoscopic diagnosis of this condition.