A 3-year-old male koala (Phascolarctos cinereus) was evaluated because of severe acute respiratory distress. Despite medical treatment, the koala died. Gross and histologic lesions consistent with acute bacterial pneumonia were identified at necropsy and Bordetella bronchiseptica was isolated from pulmonary tissue. There are 2 prior reports from Australia of fatal B bronchiseptica pneumonia in captive koalas.