Respiratory bronchiolitis-associated interstitial lung disease is one of the smoking-related interstitial lung diseases. Histopathologically, it shows respiratory bronchiolitis, which is characterized by the accumulation of pigmented macrophages within the respiratory bronchioles, accompanying peribronchiolar inflammation. Clinically, it is presented with respiratory symptoms such as a cough, sputum and dyspnea on exertion. It is well known that the incidence of malignancy in interstitial lung disease is high, but in respiratory bronchiolitis-associated interstitial lung disease the report of accompanying malignancy is rare. Here we report a case of a 60-year-old male heavy smoker presented with a cough, sputum and clubbing finger. A chest computed tomography (CT) of the patient did not show any shadow suspected of malignancy, but adenocarcinoma was found on a transbronchial lung biopsy and on a surgical lung biopsy with respiratory bronchiolitis-associated interstitial lung disease.