A 44-year-old woman underwent left single-lung transplantation for end-stage emphysema due to a1-antitrypsin deficiency in January 2010. Cyclosporine, azathioprine, and prednisolone were administered for immunosuppression and antithymocyte globulin for induction therapy at the time of transplantation. Routine examination of a lung biopsy, 4 months after transplantation, showed nonspecific, diffuse interstitial inflammation with alveolar septal fibrosis. The patient's clinical status and imaging studies, consistent with nonspecific interstitial pneumonitis, which was considered as signs of acute rejection, worsened within 2 weeks, despite high-dose steroids, change of calcineurin inhibitor, and plasmapheresis. Within a few days after a single, 10-mg, intravenous dose of alemtuzumab, the patient's health improved markedly. She has remained stable for 4 months on a standard, ambulatory, posttransplant antirejection drug regimen. We have since successfully treated with alemtuzumab three additional patients who developed interstitial lung injury after lung transplantation, who are also summarized in this report.