Gastric ulcer bleeding in neonatal period, mainly in preterm newborn babies or in neonates treated in intensive care units, is relatively frequent, However the occurrence of significant gastric ulcer bleeding in healthy full term infants is unusual. We experienced a case of massive upper gastrointestinal (GI) bleeding in a 3-day-old healthy full term infant. Endoscopic examination confirmed the presence of gastric ulcerations. Treatment was initiated with transfusion and histamine 2 receptor antagonist, and the clinical signs resolved. Mother's serum antibody to Helicobacter pylori (H. pylori) was positive. We collected stool of the patient including other 17 infants in the intensive care unit. A highly sensitive semi-nested PCR for H. pylori DNA was performed, but all infants including the patient revealed negative. H. pylori infection is not related with upper GI bleeding in healthy full term infants. In conclusion, the diagnosis of upper GI bleeding in infant can be easily made by means of pediatric endoscopy, which is a simple and a well tolerated examination.