A 70-year-old man was admitted with a chief complaint of dyspnea. Chest X-ray images showed diffuse infiltrative shadows in both lungs. A chest CT scan showed diffuse non-segmental consolidation with an air bronchogram, ground-glass opacity, and possible traction bronchiectasis. The number of lymphocytes was abnormally high in the bronchoalveolar lavage fluid (BALF), and examination of a transbronchial lung biopsy specimen revealed Masson's body and bronchiolitis. Microorganisms were not present in the BALF. Drug-induced pneumonitis, caused by the Chinese herbal drug saiko-ka-ryukotsu-borei-to or valsartan or both, which he had been taking for about 3 months, was diagnosed. The patient's symptoms and the pulmonary infiltrates seen on chest radiograph diminished after these drugs were discontinued and oral prednisolone was administered.