Cancer is one of the leading causes of death worldwide. Chemotherapy-induced arrhythmia is a potential complication of treatment that confers increased morbidity and mortality. The relationship between chemotherapeutic agents and arrhythmias is poorly established. Atrial fibrillation, ventricular ectopic beats, and prolonged QTc are the most common arrhythmias suffered by cancer patients undergoing chemotherapy. The treatment of atrial fibrillation in cancer is complicated by complex drug–drug interactions and a lack of evidence guiding practice. Furthermore, the normal risk assessment scores utilized in the decision-making for anticoagulation in the normal population are not validated in the cancer population. Multiple agents are implicated in prolonging the QTc, and this can often have adverse consequences for both the patient and the treatment of their cancer. This can manifest as torsades de pointes and sudden cardiac death. It is advised that, during treatment, oncologists should have close liaison with cardio-oncologists to ensure optimum patient management.