Pericardial effusion is the abnormal accumulation of fluid within the pericardial space. This is most commonly due to neoplastic or idiopathic causes in the canine patient. A life threatening sequel to pericardial effusion is the development of cardiac tamponade. This occurs when the intrapericardial pressure exceeds that of the right atrium and/or right ventricle. The end results of cardiac tamponade are decreases in venous return, diastolic ventricular filling, stroke volume and ultimately cardiac output. As such, pericardial disorders are one of the most important causes for the development of right heart failure in dogs. This report reviews a case of pericardial effusion and subsequent cardiac tamponade in an eight year old female spayed Golden Retriever. An overview of the pathophysiology, etiologies, history, physical exam findings, diagnostic results, treatment options, and prognoses for patients with pericardial effusion and cardiac tamponade are discussed.