In this letter we report a case of Guillain-Barré syndrome associated with infectious mononucleosis. A 20-year-old woman presented to our hospital with weakness of legs and arms. She had felt weakness in her legs for three days and in arms for one day. She had one week history of pharyingitis, muscle pain, and fever. Serological data confirmed infectious mononucleosis. Electrophysiological findings and cerebrospinal fluid examinations confirmed Guillain-Barré syndrome. She was treated with immunoglobulin, methylprednisolone and acyclovir. Paresis improved five days after the end of immunoglobulin therapy. Ebstein-Barr virus infection and infectious mononucleosis must be considered among patients with Guillain-Barré syndrome.