We present a case of a fetal pancreatic cyst, a rare disease in fetal life, detected prenatally at 30 weeks' gestation by ultrasound. Routine ultrasound examination at 30 weeks' gestation by primary obstetrician showed a cyst on the fetal abdomen. Initially, the suspected diagnosis was a mesenteric cyst. Subsequent ultrasound examination at weeks 32, 36 showed a fetal retroperitoneal cyst. A 3.6 kg female neonate was born to 23 yr old woman by spontaneous vaginal delivery at 38 weeks' gestation. The fetus underwent exploratory laparotomy. Histopathologic and immunohistochemical diagnosis revealed the cyst to be a pancreatic cyst. Surgical outcome was excellent. Thus, we report this case of a pancreatic cyst detected via prenatal ultrasonography.