A 16-year-old girl with no previous cardiac problems presented to the casualty with septic shock. Investigations revealed endocarditis involving the mitral valve. At the time of surgery, she was noted to have a large left atrial appendage herniating into the left pleural cavity due to partial absence of the pericardium. Complete or partial absence of the pericardium is an uncommon congenital anomaly. Though various complications and presentations are reported, it has not been identified as a risk factor for endocarditis. We discuss the possible mechanism, and need for prophylaxis against endocarditis, in patients with absence of the pericardium.