West Nile virus (WNV) infections may trigger febrile conditions and/or neuroinvasive disease in a portion of the exposed individuals. Serosurveillance data from various regions of Turkey indicate WNV activity. The aim of this study was to confirm the antibody specificity of the serum samples via virus neutralization assay, previously reported to be reactive for WNV IgM. The samples originated from two individuals with the preliminary diagnosis of aseptic meningitis/encephalitis of unknown etiology in 2009 and had been classified as probable WNV infections. Cerebrospinal fluid and sera samples of these patients had been evaluated as negative for WNV RNA and IgG antibodies. Only one serum sample could be included in the neutralization assay due to the limited amounts in the current investigation. The sample was observed as positive in dilutions of 1/20 and 1/40, thus confirming the diagnosis of WNV-related central nervous system infection in a 62 year-old female patient from Ankara, Central Anatolia, Turkey.