We report a case of unsuspected difficult intubation in an adult due to anatomical abnormalities caused by a thermal burn injury on the right anterior pillar of the pharynx. After induction of anesthesia, vocal cords and epiglottis were not seen and the right half of the pharyngeal cavity was obstructed by a narrowed palatoglossal arch on the laryngoscopic view. Endotracheal intubation trials failed by oral and nasal routes. The laryngeal mask airway could not be passed into the narrowed oropharynx. We awaked the patient and took the patient's past history precisely and an otolaryngologic evaluation was taken. We found that at the age of six, the patient experienced a thermal burn injury on the right anterior pillar of the pharynx by heated iron and anatomical deformities by scar contracture formed thereafter. The next day a partial palatoglossal resection was done in sitting position under local anesthesia and then endotracheal intubation by direct laryngoscopy could be completed successfully.