Transthoracic epicardial catheter ablation is a useful supplemental or even preferred strategy to eliminate cardiac arrhythmias in the electrophysiology laboratory. The indication for this technique has extended to a diverse range of cardiac arrhythmias, including scar-related ventricular tachycardia (VT), idiopathic VTs, accessory pathways, atrial tachycardias, inappropriate sinus tachycardia, and atrial fibrillation, as the epicardial substrates of these tachyarrhythmias have become increasingly recognized. When endocardial ablation and epicardial ablation through the cardiac veins are unsuccessful, transthoracic epicardial ablation should be the next option. Intrapericardial access is usually obtained through a subxiphoidal pericardial puncture. This approach might not be possible in patients with pericardial adhesions caused by prior cardiac surgery or pericarditis. In such cases, a hybrid procedure involving surgical access with a subxiphoid pericardial window and limited anterior or lateral thoracotomy might be a feasible and safe method of performing epicardial catheter ablation in the electrophysiology laboratory. Potential complications associated with this technique include bleeding and collateral damage to the coronary artery and phrenic nerve. Although the risk of these complications is low, electrophysiologists who attempt epicardial catheter ablation should know the complications associated with this technique, how to minimize their occurrence, and how to rapidly recognize and treat the complications that they encounter. This review discusses the indications, techniques, and complications of transthoracic epicardial catheter ablation.