We report about a 57-year-old patient suffering from the typical symptoms of normal-pressure hydrocephalus (NPH) including gait disturbance, urinary incontinence, and mental deterioration. CSF analysis established the diagnosis of chronic active Lyme neuroborreliosis with lymphocytic pleocytosis and intrathecal Borrelia burgdorferi antibody production. After several weeks of i.v. antibiotic treatment we observed normalization of CSF parameters as well as a clear improvement of clinical symptoms so that surgical shunting was no longer indicated. Interference with subarachnoid CSF flow may be a possible cause of the observed symptomatic NPH in a patient with chronic Lyme neuroborreliosis.