An adult, wild-collected, male harp seal (Phoca groenlandica) was transferred from a rehabilitation center to a display facility because of unilateral phthisis bulbi and decreased use of the right forelimb, which precluded its release. In quarantine, the animal demonstrated limited use of the right forelimb, which acutely progressed to complete disuse of the limb accompanied by intermittent lethargy. One month after transfer, the animal was found dead on exhibit. Necropsy showed septic arthritis of the right scapulohumeral joint, valvular endocarditis with systemic bacterial thromboembolism, and infarction of the cerebrum and myocardium. Culture of the blood and affected joint space revealed Staphylococcus aureus. Bacterial polymerase chain reaction of formalin-fixed tissues from the heart and brain were also positive for S. aureus. Staphylococcus aureus infection should be considered as an additional cause of endocarditis and embolic encephalitis in seals.