Catheter ablation is an established treatment for atrial fibrillation (AF). The incidence of major complications related to the procedure is reported to be 4.5%, and delayed cardiac tamponade (DCT) is a rare, although recently recognized, complication. However, the mechanisms underlying the development of DCT remain unclear. We herein report the cases of two men, both 49 years of age, who developed cardiac tamponade requiring pericardiocentesis a few weeks after undergoing pulmonary vein isolation for persistent AF. Physicians should explain to the patient the potential for DCT as a complication prior to performing catheter ablation and provide careful follow-up for at least a few weeks after the session.