A 39-year old man was admitted to our hospital with a chest stab wound. The stab wound was approximately 3 cm long by 4 cm deep and located in the subxiphoid process area. Neither the pleura nor pericardium were involved. However, pneumopericardium was detected by posteroanterior chest x-ray and computed axial tomography. The patient was treated by conservative therapy, and the pneumopericardium spontaneously disappeared after 5 days. The patient was discharged on hospital day 7.