Report of a case of a mycotic pseudoaneurysm of the ascending thoracic aorta occurring in the absence of surgical or blunt trauma in a patient who presented with purulent pericarditis. Surgical pericardial drainage was required, which revealed Staphlococcal aureus. Subsequent transesophageal echocardiogram demonstrated a 4 cm x 4 cm pseudoaneurysm of the posterior wall of the aorta above the sinotubular junction. The patient refused surgical correction of the aortic pseudoaneurysm and was successfully managed with antibiotic therapy.