A 56-year-old man presented with chest discomfort on emergency room. He had stroke 8 years ago and right upper lobectomy (lung cancer, adenocarcinoma) with lymph node dissection 2 weeks ago. Electrocardiogram revealed normal sinus rhythm without any ischemic signs but chest radiograph showed pleural effusion at right lobe and pneumopericardium at left heart border (Figure 1). Computed tomography (CT) showed pneumopericardium at anterior side but no sign of bronchopericardial fistula (Figure 2). Two-dimensional transthoracic echocardiogram was visible only in diastolic phase (Figure 3) but hindered by trapped pericardial air in systolic phase (Figure 4). It could be ``blinking heart sign` in echocardiogram of pneumopericardium, especially in early phase at parasternal long view and parasternal short view. We could not find any compromised-hemodynamic sign and remarkable abnormality. Chest tube was inserted for drainage of right pleural effusion and pleural fluid analysis revealed chylothorax. So we presumed that pneumopericaridum resulted from the sequela of post lung cancer operation. During conservative care with chest tube drainage and intermittent nasal oxygen therapy, his symptoms did not aggravate and his vital signs were stable. After improvement in pleural effusion and pneumopericardium, chest tube was removed. The patient was discharged in good condition and has subsequently done well.