The case of a 9-year-old Schnauzer male canine with a history of lack of appetite, lethargy and exercise intolerance is reported. Echocardiography was performed identifying pericardial effusion and a neoplastic mass in the pericardium. The patient presented cardiac tamponade, which was treated with pericardiocentesis. Once the patient was stabilized, a subphrenic partial pericardiectomy was performed, removing the neoplastic