A 46-year-old man was admitted to our hospital with cough and dyspnea on exertion. A chest X-ray film showed diffuse interstitial shadows. He had hyperpigmentation forming a network pattern around his neck and dystrophy of the fingernails and toenails, and was diagnosed as having dyskeratosis congenita. Histological examination of the lung specimen obtained from the left S4b by open lung biopsy revealed usual interstitial pneumonia pattern with neither asbestos bodies nor silicotic nodules. Taken together with previously published findings, pulmonary involvement is considered to be an important complication of dyskeratosis congenita.