A teratoma is the most common germ cell tumor in children; however, a gastric teratoma is very rare. An immature gastric teratoma has malignant potential; therefore, it should be removed surgically and followed up routinely to assess for recurrence by performing imaging studies and estimating serum alpha-fetoprotein (AFP) level. We describe the case of a 2-day-old male neonate with abdominal distension and a palpable mass. He underwent surgical resection of a tumor that was diagnosed as an immature gastric teratoma.