Although thoracopagus twins joined at the upper chest are the most common type of conjoined twins, the separation surgery in these cases has a higher mortality rate. Here, we describe an anesthetic management approach for the separation of thoracopagus conjoined twins sharing parts of a congenitally defective heart and liver. We emphasize the importance of vigilant intraoperative hemodynamic monitoring for early detection of unexpected events. Specifically, real-time continuous monitoring of cerebral oximetry using near-infrared spectroscopy allowed us to promptly detect cardiac arrest and hemodynamic deterioration.