An 80-year-old woman was referred to our hospital due to the presence of a mass that was identified on a chest X-ray. A further investigation demonstrated advanced adenoid cystic carcinoma of the lungs. Anti-cancer chemotherapy with docetaxel was carried out and the lesion remained as stable disease. Subsequently, pleural effusion was detected, and an investigation of the pleural effusion revealed the existence of malignant cells with an epidermal growth factor (EGFR) mutation. Gefitinib was administered and the pleural effusion resolved. This is the first case of a positive EGFR mutation of adenoid cystic carcinoma of the lung with a favorable response to an EGFR-tyrosine kinase inhibitor.