This chapter provides a comprehensive overview of the various monitoring techniques employed during cardiopulmonary bypass (CPB) to ensure patient safety and the success of the procedure. Given its complexity and potential risks, CPB, a critical component in many cardiac surgeries, demands rigorous monitoring. The discussion spans various monitoring modalities, with a particular focus on essential techniques, such as hemodynamic monitoring, which includes arterial and venous pressure, heart rate, and cardiac output. Additionally, it underscores the critical role of continuous electrocardiogram (ECG) monitoring in detecting arrhythmias and ischemic changes. It also highlights advanced methods such as transesophageal echocardiography (TEE) for their capacity to provide real-time assessments of cardiac function and structure. The narrative emphasizes the importance of monitoring blood gases and acid–base balance—a key factor in managing metabolic status during CPB. It includes a brief overview of arterial blood gas analysis, oxygen saturation, and alpha-stat and pH-stat strategies. It also discusses cerebral oximetry and near-infrared spectroscopy (NIRS) as tools for evaluating cerebral oxygenation, aiming to mitigate neurological deficits. Temperature management is another critical aspect covered, which highlights the methods and importance of maintaining appropriate body temperature during CPB.