The production of indium compounds to manufacture liquid crystal displays has recently increased. This is concerning because inhaled indium can cause pulmonary toxicities like interstitial pneumonia and emphysema. Carcinogenesis associated with indium exposure has been demonstrated in animal experiments; however, limited reports exist for humans. Here, we present a case of lung cancer that developed in a 46-year-old man diagnosed with interstitial pneumonia owing to indium lung disease 16 years ago after occupational exposure to indium-tin oxide for 12 years. The patient also had a history of interstitial pneumonia exacerbation 6 years ago. He visited our hospital with complaints of left-sided chest discomfort. Chest X-ray revealed a mass shadow in his left-sided upper lung with left-sided pleural effusion. He was subsequently diagnosed with lung adenocarcinoma with pleural dissemination following video-assisted thoracic surgery and pathological examination. Moreover, pulmonary fibrosis and cholesterol granulomas were noted, consistent with indium lung disease. Although serum KL-6 and indium levels decreased slowly, they remained at 1,460U/mL and 9.97ng/mL, respectively. Since exposure to high indium levels can induce lung cancer, we need to be aware of the complication of lung cancer, particularly in individuals with interstitial pneumonia.