Constrictive pericarditis occurs when either the visceral, parietal or both layers of the pericardium become thickened, fibrotic and inelastic. The constriction on the heart prevents appropriate ventricular filling resulting in decreased cardiac output and clinical signs of right heart failure1 This disease primarily affects middle aged-older, large-breed dogs, with Golden Retrievers being overrepresented. There are several etiologies including trauma, infectious diseases, idiopathic constrictive pericarditis and neoplasia. Neoplasia, especially hemangiosarcoma of the right atrium and heart base tumors, is most common, followed by idiopathic constrictive pericarditis, which is a diagnosis of exclusion. Features of this disease include respiratory variation in ventricular filing, interventricular dependence, and augmented longitudinal motion of the heart on echocardiogram. Palliative surgical pericardiectomy is indicated to relieve the constriction of the heart. Definitive diagnosis and prognosis is based on histology.