Acute pericarditis is the most common disease of the pericardium encountered in clinical practice. It is diagnosed in 0.1% of all admissions and 5% of emergency room admissions for chest pain. In developed countries, it is usually due to a benign cause. Idiopathic and infectious pericarditis are more common than secondary to surgical pericardiotomy or neoplastic causes, whereas tuberculosis is the dominant cause in developing countries. The most common symptoms of pericarditis are characteristic chest pain and fever. Since pericarditis presents a benign outcome because of self-limiting and good response to conventional anti-inflammatory therapy, it can be safely managed on outpatient basis unless a specific cause is suspected or the patient has high-risk features to avoid complications such as pericardial effusion, cardiac tamponade or recurrent pericarditis. We report a case of pericarditis, diagnosed 9 months after surgical closure of an atrial septal defect, in a 7-year-old boy with favorable evolution.