Dermoid tumor in the eustachian tube (DTIET) is a congenital disease. Our patient had the symptom of discharging pus in the left ear when he was about 1 year old. Due to lack of understanding of the disease at that time, he was misdiagnosed as having cholesteatoma, for which he underwent three surgical operations in the middle ear. Recently, with detailed preoperative imaging estimation and full consideration of surgical risks, under the guidance of TV, using oto-endoscopes and nasal endoscopes jointly, the DTIET was resected completely via the combined approach of pharyngeal and tympanic openings of the eustachian tube. This case indicated again that it was a space-occupying lesion in the eustachian tube. On the basis of the characteristic expressions of CT and MRI, the possibility of DTIET should be fully considered. Endoscopic technology has advantages for surgical operation in the eustachian tube, which might remove the mass and achieve the aim of minimal trauma.