We report herein a rare case of choledochal cyst diagnosed at 14 weeks gestation and treated with percutaneous transhepatic drainage until postpartum. A 26-year-old primigravid woman at 14 weeks gestation presented with epigastric pain, slight fever, and nausea of 3 days duration. Abdominal ultrasonography revealed a 6-cm-diameter cystic mass between the porta hepatis and the pancreas head, which was diagnosed as a type I choledochal cyst. At 18 weeks of gestation, her upper abdominal pain became severe, and the size of the choledochal cyst increased to 12 cm in diameter. Laboratory data revealed a biliary obstruction. Percutaneous transhepatic drainage was performed immediately. She delivered a healthy male baby by elective cesarean section at 37 weeks of gestation. At 6 weeks postpartum, the patient underwent surgical excision of the choledochal cyst, cholecystectomy, and formation of a Roux-en-Y hepaticojejunostomy. Although choledochal cysts are rare during pregnancy, obstetricians should be familiar with the condition to ensure prompt diagnosis and adequate definitive management, given that the implications of missed or delayed diagnosis may be detrimental to both mother and fetus.