Choledochal cysts (CCs) are congenital dilatations of extrahepatic and/or intrahepatic bile ducts. It is a rare biliary entity, in the Asian population, the incidence can be as high as 1:1000 live. We reported case of One-month old baby girl with yellowish skin and acholic stool the baby has been suspected with anechoic abdominal mass at 17 weeks of gestational age using fetal ultrasound. From physical examination, jaundice was seen on the sclera and all over the body. The bowel sound was normal, without distention, without palpable liver nor spleen. The mass was not palpable either. Aspartate transaminase serum (AST), alanine aminotransferase serum (ALT), gamma glutamyl tranferase (GGT), bilirubin level was increased. Ultrasound was performed and revealed extrahepatic dilation to form a saccus in the proximal CBD, according to the picture of type 1 choledocal cyst. The surgeon performed cyst excision and hepatoduodenostomy procedure and found choledochal cyst. Histopathologic examination from cyst confirmed the choledochal cyst. The patient was discharged in good condition. We conclude that Type I choledochal cysts can be identified prenatally during a detailed fetal sonogram. The newborn should be investigated to confirm the diagnosis and undergo cyst excision promptly to reduce the potential for complications.