A 3-year-old female jaguar (Panthera onca onca) died after having 1 day history of respiratory failure. At necropsy, the pericardial sac contained large amounts of cloudy fluid enriched with fibrin. Numerous yellowish nodules, which are variable in size and often confluent, are randomly scattered throughout the myocardium. Pasteurella haemolytica was isolated from the pericardial sac and myocardium. In the lung, severe pulmonary congestion, edema and vasculities with intralesional presence of heartworm were found. Therefore the cause of death in this jaguar is believed to be due to respiratory failure following concurrent heartworm infection and bacterial pericarditis and myocarditis.