A 68-year-old woman developed delayed QT prolongation and Torsades de Pointes (TdP) following electrical cardioversion for atrial fibrillation. Despite early discontinuation of Sotalol and optimal electrolyte replacement, she experienced bradycardia-associated TdP approximately 66 h post-cardioversion, requiring resuscitation and temporary overdrive pacing. QTc normalised with pacing, and no further episodes occurred. This case highlights a vulnerable window for proarrhythmia in the days following cardioversion, particularly in patients with multiple QT-prolonging risk factors. Extended ECG monitoring and consideration of early pacing may be critical in preventing life-threatening arrhythmias in high-risk individuals.