Objective: To summarize the clinical manifestations, imaging characteristics and experience of surgical treatment of tethered cord syndrome (TCS) accompanied by dermal sinus tract (DST) in adulthoods. Methods: The authors retrospectively analyzed a series of 25 adult patients with TCS due to DST that were surgically treated under microscope from September 2010 to October 2019. There were 10 males and 15 females with an average age of 29.7 years (rang, 18-48 years). Characterized cutaneous malformation and dermal sinus were found in the lumbosacral region in all the 25 patients. Clinically, all the patients presented with chronic back and lower-extremity pain, numbness and weakness of lower limbs, and bowel and bladder dysfunction. Two cases were admitted to the emergency room with acute infectious cerebral spinal fluid (CSF) leakage complicated with meningitis. According to magnetic resonance imaging (MRI) images, the subdural course of DST whose traction of the spinal cord, the location of the conus medullaris, the presence of subdural lesions, and the diameter of the internal filum terminale were evaluated. The surgical procedure included separating and excising of the DST, section of the internal filum terminale, detethering of the TCS, and reconstruction of the dural sac under microscopy. The patients remained in prone position in 7 days postoperation. Results: MRI showed that the position of the conus medullaris was lower than the level of lumbar 2 vertebrae, and the distal part of the DST entered the subdural stretched part of the spinal cord, to constitute one of the factors of TCS in all the 25 patients. Twenty patients had fatty infiltration of internal filum terminale and another patient had thickened (approximately 5 mm in diameter) internal filum terminale resulting in tightening the conus medullaris. A total of 25 operations were performed including completely dissection and resection of the DST through the skin down to the subdural space, section of the internal filum terminale, detethering of the TCS, and the subdural dermoid cysts were removed in two patients. There were no postoperative complications. The postoperative pathology was consistent with the structure of the DST and internal filum terminale. The local pain was relieved, and the lower-extremity weakness and bowel and bladder dysfunction were gradually relieved postoperatively. The period of follow-up ranged from 3 months to 9 years (mean, 3.9 years). The neurological function of all the patients was intact, and MRI showed that the physiological curvature of the thoracolumbar spine remained normal. There was no recurrence of TCS observed during the follow-up. Conclusion: The adult TCS accompanied with DST is characterized by typical cutaneous malformation in the lumbosacral region and tethering of the spinal cord. The patients are usually combined with internal filum terminale enlargement tightening of conus medullaris as well. The surgical treatment including totally resection of the DST and section of the internal filum terminale to detethering the TCS at the same time under microscopy. The outcome of surgical treatment is satisfactory.