A 6-year-old male blue-and-gold macaw (Ara ararauna) was presented with severe weakness, anorexia, and weight loss of 2 weeks duration. Cardiac auscultation revealed a soft systolic murmur. Blood cultures collected both antemortem and postmortem yielded pure isolates of Enterobacter cloacae. At necropsy, vegetative endocarditis was found involving the left atrioventricular valve. Microscopically, the lesion on the valve was characterized by a mixture of necrotic material, colonies of gram-negative bacteria, fibrosis, and inflammatory infiltrate consisting primarily of heterophils.