Fetus-in-fetu is a rare congenital anomaly which a fetiform mass as a monozygotic twin often in the abdomen of its twin. We report a case of a newborn girl presented with a monster-like mass at the base of the coccyx at birth, known as sacrococcygeal fetus-in-fetu. After delivered, the baby experience with critical asphyxia, hypovolemic shock and cardiac arrest. With effective multidisciplinary team, the mass was successful removed and the baby well survived. This report presents the clinical presentation, diagnosis, management, and clinical of the case.