Sick sinus syndrome (SSS) is an abnormality of sinus nodal impulse formation by intrinsic or extrinsic causes. Patients with SSS often are asymptomatic, or have mild or nonspecific symptoms, including dizziness, palpitations, fatigue, and confusion related to the decreased cardiac output. SSS can rarely cause conditions like syncope, congestive heart failure, thromboembolism, pulmonary edema, cardiac arrest, or sudden death. We report here on a severe bradycardia during general anesthesia for aneurysmal clipping and tachycardia-bradycardia syndrome followed by cardiac arrest postoperatively in the ICU, which was subsequently diagnosed as SSS with 24-hour Holter monitoring.