A 69-year-old woman suffering for two weeks from dry cough and progressive dyspnea on exertion was admitted to our hospital. Three weeks prior to admission, the patient had ingested a Chinese herbal medicine, Kakkon-to, to treat her upper respiratory tract infection. Chest computed tomography revealed patchy consolidation in both lungs. We suspected drug-induced lung injury caused by Kakkon-to, and steroid pulse therapy comprising the intravenous infusion of 1 g/day methylprednisolone was subsequently initiated. Following the therapy, her symptoms, radiological findings, and hypoxia showed immediate signs of improvement. Drug-induced lymphocyte stimulation and basophil activation tests performed on her peripheral blood sample were positive for Kakkon-to, but negative with the control drug. Based on these findings, a diagnosis of Kakkon-to−induced lung injury was made. To the best of our knowledge, this is a second report of Kakkon-to−induced lung injury. Moreover, the basophil activation test had been suggested to be a useful tool in identifying Kakkon-to as the cause of her injury.