A 51-year-old man with no underlying disease was referred to our hospital, complaining of mild headache. In May 2004 he developed headache of sudden onset in the occipital region and neck pain. He visited our hospital the following morning. At the first visit, there was no fever and only an analgesic was prescribed. The headache alleviated, with only occasional mild episodes thereafter. However, 2 days later, the headache aggravated again, associated this time with elevated body temperature (38 degrees C). The patient visited our hospital and a lumbar puncture was performed; examination of the cerebrospinal fluid revealed marked elevation of the cell count (mononuclear cell-dominant). The patient was admitted to the hospital and started on treatment with cefotaxime and acyclovir. However, the symptoms persisted and 10 days later, the cerebrospinal fluid culture yielded a growth of Campylobacter jejuni (C. jejuni). The antibiotic was therefore changed to panipenem, which resulted in prompt resolution of the symptoms. To the best of our knowledge, meningitis caused by C. jejuni in an immunocompetent adult is extremely rare. This case highlights the importance of bearing in mind the possibility of C. jejuni meningitis in a patient of meningitis associated with mononuclear cell-dominant pleocytosis of the cerebrospinal fluid.