Gastric duplication is a rare anomaly which account for only 3.8% of all gastrointestinal duplication. Gastric duplications are usually cystic lesion without communication with lumen. Most frequent presentation is an abdominal mass with vomiting, mainly diagnosed within the first year of life. Surgical removal is necessary in all cases, and optimal timing for surgery is the time that diagnosis is made. However, prenatally diagnosed gastric duplication is getting more common, and determining timing for surgery is not easy due to absent or minimal symptoms just after birth. We experienced prenatally diagnosed gastric duplication in a female newborn baby that gastric duplication was suggested in $24^{th}$ week of gestational age through prenatal ultrasonogram. Surgical removal was done at 3 months after birth, and showed good results. We think that natural history of gastric duplication and prevalent age of surgical disease which is similar to gastric duplication such infantile hypertrophic pyloric stenosis should be considered when timing of surgery on prenatally gastric duplication is decided.