Congenital adult tethered cord syndrome (TCS) with accompanying lipoma is a rare disease in adults and difficult to diagnose. Surgical treatment is difficult and can lead to many complications. The authors present a case of a 26-year-old woman with a large filium terminale lipoma and tethered cord at the S2 level. The patient complained of pain in the lumbosacral region of the spine, moderate incontinence, and a right-sided foot drop with impaired sensation. Diagnostics were performed using magnetic resonance imaging (MRI). The patient underwent a surgical procedure untethering the spinal cord with a partial lipoma resection. Microsurgical techniques were used during the procedure and intraoperative neurophysiological monitoring was performed. In the postoperative observation, the pain in the lumbosacral region of the spine was reduced, and some of the sensory disturbances subsided. However, there was no significant improvement in the foot muscle strength. Long-term symptoms such as lumbosacral pain, sensory disturbances and poor urinary incontinence are not characteristic symptoms that clearly indicate tethered cord syndrome. Surgical treatment in this case is a difficult procedure due to the nature and location of changes in the environment of the cauda equina. Another serious problem is identifying the filium terminale. Surgical operation is associated with postoperative fluid fistula with impaired surgical wound healing. The outcome of the surgery is not always satisfactory for the patient, as the only treatment effect can be to stop the progressive neurological symptoms.