Gastric outlet obstruction (GOO) results from obstructing lesions in the region of the pyloric channel. In neonates, hypertrophic pyloric stenosis (HPS) is the most common cause while peptic ulcer is a rare cause. Neonatal gastric ulcer is relatively frequent in preterm newborn babies or in neonates treated in intensive care units. In healthy neonates, mucosal ulcers are associated with stressful conditions. In gastric ulcer diseases, gastric outlet obstruction is usually caused by a combination of edema, spasm, fibrotic stenosis and gastric atony. We experienced a case of neonatal gastric ulcer with a large hematoma in a 3-day-old infant presenting with repeated vomiting, poor oral intake, and abdominal distension. For the differential diagnosis, we did abdominal ultrasonography. Hematoma was diagnosed by abdominal ultrasonography. Endoscopic examination confirmed the hematoma and the presence of gastric ulcerations. We report this case with a brief review of the literature.