Sacrococcygeal teratoma is the most common germ cell tumor in newborn infants. Teratomas with unknown etiology can cause problems in the management of surgery and anaesthesia during operation since they can reach high pressure levels due to increased blood supply. A sacrococcygeal teratoma was diagnosed with prenatal ultrasound and a 4050 g 40 week newborn, was born with C/S. The physical examination was unremarkable except for a solid mass the size of 15x10 cm in the sacrococcygeal region. Preoperative anaesthesia examination of the case was within normal limits and at the second day of her life the mass was excised. The invasive arterial and central venous pressures with esophageal temperature monitorization was assured and severe bradycardia, hypotension, and hypoxemia developed during the operation. With close invasive monitorization, the changes were realised immediately and treated effectively. The importance of invasive arterial and venous pressure monitoring in patients operated on during the neonatal period with giant sacrococcygeal teratoma, is highlighted in this report.