Giant mediastinal mass tumors have been associated with perioperative respiratory and circulatory life- threatening complications during induction of general anaesthesia and initiation of positive pressure ventilation leading to sudden cardiac arrest known as MMS, ‘Mediastinal mass syndrome’ (4, 5,6). A detailed meticulous preanaesthetic evaluation and a well thought out anaesthetic plan can avoid life-threatening events during management of these patients. We report a successful anaesthetic management of a 12 yrs old pediatric patient with a left sided giant mediastinal germ cell tumor, posted for complete surgical resection. We followed the guiding principles for anaesthetic management of such cases, maintaining propped up position, avoiding muscle relaxants, maintaining spontaneous breathing, keeping cardiac team and perfusion team ready to cannulate and institute CPB in case of sudden cardiorespiratory collapse, adapting to low volume ventilation and titrated and step wise induction of anaesthesia.