We present a case of a rapidly progressive pseudomembranous tracheobronchitis and pneumonia in a 52-year-old woman with severe aplastic anemia. Bacillus cereus was isolated from bronchoalveolar lavage fluids, blood cultures, and pseudomembrane biopsy specimens; despite intensive antibiotic treatment, the patient's condition deteriorated rapidly. To our knowledge, this is the first report of a B. cereus infection that has caused pseudomembranous tracheobronchitis, possibly because of the production of bacterial toxins.