QT prolongation and QT dispersion (QTd) are key electrocardiographic markers for assessing cardiotoxicity, particularly in drug-induced cardiac complications. QT prolongation, characterized by an extended QT interval, indicates delayed ventricular repolarization, increasing the risk of severe arrhythmias such as Torsades de Pointes. QT dispersion, defined as the difference between the longest and shortest QT intervals recorded across ECG leads, reflects regional variations in repolarization and indicates electrical instability and arrhythmogenic potential. Drug-induced cardiotoxicity is a significant concern, particularly with chemotherapeutic agents, antipsychotics, and certain antibiotics. The primary mechanism involves inhibiting potassium ion channels, leading to prolonged repolarization and increased susceptibility to arrhythmias. Given these risks, continuous ECG monitoring and effective risk stratification are essential for patients receiving QT-prolonging therapies. Modern cardiologists must recognize the cardiotoxic effects of conventional and emerging therapeutic agents, including chemotherapy, targeted therapies, and immunotherapies. A multidisciplinary, collaborative approach is essential for optimizing cardiovascular health in patients undergoing treatment for various conditions. This strategy ensures that potentially life-saving therapies are administered safely while minimizing the risk of cardiotoxicity.