Congenital cystic adenomatoid malformation (CCAM) is a rare condition which is easily detectable by prenatal ultrasonography. Fetuses with large CCAMs associating with hydrops are predisposed to perinatal mortality, therefore prenatal intervention is required. While macrocystic CCAM is treated prenatally by thoracentesis or thoraco-amniotic shunt, microcystic or mixed CCAM is difficult to manage in the fetus. In these latter lesions, fetal lobectomy, sclerotherapy, or laser ablation was used to treat lesions directly. We present an unusual prenatal case of mixed CCAM associating with hydrops and marked ascites, which was conservatively managed with prenatal abdomino-amniotic shunting and successfully treated by postnatal surgery.