Cardiac herniation is a rare but potentially fatal complication of intrapericardial pneumonectomy. It usually occurs within the first 24 hours postoperatively. Symptoms are side-related. It has a sudden onset and invariably evolves to cardio-vascular collapse. Clinical suspicion combined with plain chest X-ray and electrocardiographic changes must lead to a quick diagnosis. Definitive treatment requires prompt surgical action. Closure of the pericardial defect during initial operation does not exclude the possibility of cardiac herniation. We present a patient with a right-sided cardiac herniation after intrapericardial pneumonectomy. Patient was treated surgically and survived.