A 71-year-old male was admitted to the hospital complaining of cough. The chest X-ray and computed tomography (CT) revealed a large tumor in the right lower lung, which was diagnosed as poorly differentiated adenocarcinoma. As the tumor grew rapidly and caused obstructive pneumonia, right middle and lower lobectomy was performed even if right gingival tumor was suspected as metastasis from lung tumor. The patient complicated with aspiration pneumonia after operation and died on the 20th postoperative day. The prognosis of lung cancer with gingival metastasis is very poor. Early detection and appropriate therapy is necessary.