The reported annals incidence of pericardial cysts (PC) in medical literature varies from 1/100000 to 1/120000. They are usually incidentally found during a thoracic or cardiac surgery or by an imaging modality by chance or remain clinically asymptomatic until the 3rd or 4th decades of life. However, in rare cases, compression or rupture of cysts into the surrounding structures, lead to the appearance of symptoms that may further be diagnosed by imaging modalities. We report the case of a 35-year-old man, with presentation of palpitation and chest pain and dyspnea. A transthoracic echocardiography (TTE) and computed tomography (CT scan) confirmed the presence of a cystic lesion the in right lower cardiac border. With the impression of a hydatid cyst, he has undergone open cardiac surgery and during mediastinal exploration a well-defined cyst filled with pasty and thrombotic materials was found intrapericardialy that was attached to the right atrial wall. The cyst with the inflammatory thick wall was enblockly resected. In the histological examination, diagnosis of pericardial cyst was confirmed. The postoperative phase was uneventful and during 6 months of follow-up he was good with no pericardial effusion on TEE.