Monitoring is the foundation of safe anesthetic practice, enabling early detection of physiological disturbances and timely intervention. Advances in monitoring have contributed to the dramatic decline in anesthesia-related morbidity and mortality. The American Society of Anesthesiologists mandates minimum monitoring standards for all anesthetics, oxygenation, ventilation, circulation, and temperature, which are irrespective of the anesthetic type or setting. Beyond these, anesthesiologists employ a wide range of advanced modalities tailored to patient comorbidities, surgical complexity, and intraoperative risk. Invasive hemodynamic monitoring (e.g., arterial lines, central venous catheters, pulmonary artery catheters, etc.) guides fluid therapy, vasopressor use, and resuscitation in high-risk patients. Neuromuscular monitoring ensures safe administration and reversal of neuromuscular blocking agents, reducing the risk of postoperative respiratory complications. Depth of anesthesia monitors, such as the bispectral index, provide adjunctive data to help reduce the risk of awareness and overly deep anesthesia, though their effect on outcomes remains debated. Point-of-care ultrasound and transesophageal echocardiography represent modern expansions of anesthetic monitoring, offering real-time visualization of cardiac, pulmonary, and vascular structures. Additionally, intraoperative urine output monitoring provides valuable information about renal perfusion and fluid balance in select cases. For internists, understanding anesthesia monitoring is essential: many postoperative complications, such as myocardial injury, delirium, hypoxemia, and renal dysfunction, reflect intraoperative physiology captured by these modalities. Ultimately, anesthetic monitoring complements but does not replace clinical judgment and vigilance. Familiarity with monitoring principles allows internists to better interpret postoperative complications, collaborate effectively with anesthesiologists, and contextualize perioperative risk discussions for patients.