We report an atypical case of cat scratch disease (CSD), accompanied with encephalopathy that is a rare complication of CSD. A 17-year old man consulted a doctor for his right axillary lymphadenopathy. The history of his contact with cats and the sign of lymphnode swelling and fever suggested a suspect of cat scratch disease. Administration of ampicillin improved his clinical symptoms, but a few days later he suddenly fell into coma after an episode of convulsion. The CT scan of the brain and laboratory tests showed no significant findings except the slightly elevated cell counts and concentration of protein in his cerebrospinal fluid. He was referred to our hospital on the next day for further examinations and treatments for his coma of unknown cause. The physical examination on admission revealed slight neck stiffening and hypertonicity of his right lower limb, but radiological and laboratory tests showed no significant findings. He gradually recovered from his coma without apparent sequelae in three weeks. Indirect fluorescence antibody titers for CSD in his serum showed a significant elevation to 1:160 of IgM and 1:512 of IgG, and his clinical features were compatible to these of CSD with complications of the central nervous system.