Pericarditis is an inflammation of the pericardial space precipitated by various factors in different species of veterinary interest. Classic veterinary syndromes involving pericarditis include traumatic reticuloperitonitis, or hardware disease, in cattle, and polyserositis in pigs. This case report discusses a fatal incident of pericarditis in a horse. The carcass of the horse was examined using standard necropsy and histopathological techniques and the cause of death was attributed to heart failure precipitated by fibrinoconstrictive epicarditis and pericarditis. The disease in this horse was likely related to systemic infection with Streptococcus zooepidemicus. Heart diseases, particularly congestive heart failure, are uncommon in horses and pericarditis is rarely reported in this species. This case demonstrated signs of an insidious onset of pericarditis that, if it detected earlier, may have been amenable to treatment.