A 50-year-old male complaining of a dry cough was admitted to our hospital. Chest X-rays showed reticulonodular shadows in the bilateral lower lung fields, and video-assisted thoracic surgery was performed. We first suspected this case to have desquamative interstitial pneumonia (DIP) coexisting with nonspecific interstitial pneumonia (NSIP). The patient had glaucoma; therefore we were hesitant to start steroid therapy and urged him to stop smoking. He was unable to, however, and thereafter showed a progression of imaging features and an increase in KL-6 level. High levels of serum IgG4 and IgG4-positive plasma cell infiltration of the lungs were observed. As a result, the patient was started on prednisolone after consulting an ophthalmologist. The imaging features and the KL-6 level showed improvements. The prednisolone was thus tapered gradually in an outpatient setting, and the patient has been healthy without relapse. We ultimately diagnosed this case to have IgG4-related lung disease associated with DIP-like features in a heavy smoker.