Gastric teratoma is an extremely rare tumor that accounts for less than 1% of all teratomas. Gastric teratoma is mostly presented as a palpable abdominal mass, and is rarely accompanied with gastrointestinal bleeding such as melena or hematemesis. A 5-month-old male infant was brought with a history of pale facial color and dark-colored stool. The hemoglobin level was at 6.1 g/dL, with melena having begun 1 month previous. Upper gastrointestinal endoscopy revealed a polypoid mass with bleeding at the upper body and lesser curvature of the stomach. Wedge resection of the stomach was performed and histopathological analysis confirmed the mass to be a mature cystic teratoma. There was no recurrence after the operation during follow-up.