A 45-year-old female with oophoritis (pelvic inflammatory disease) caused by Campylobacter fetus (C. fetus) is reported. She was admitted to the hospital because of high fever and an acute abdomen. On admission, severe inflammation was observed by the laboratory findings, and abdominal X-ray and CT scan revealed ileus with marked swelling of the right ovary. Laparotomy was performed with adonexooophrectomy due to the tubo-ovarian abscesses. C. fetus was isolated from the right ovary, salpinx and ascites. Erythromycin was administered after a sensitive test of C. fetus as the bacteria was isolated at operation. She was discharged on the 17th day after her admission. Indirect immunofluorescent test with hyperimmune rabbit sera to isolated C. fetus revealed a fine to coarse granular immunoreaction in the cytoplasm of the macrophages infiltrated in the tissue. This result was interpreted as the existence and growth of bacteria in the right ovarian tissue. Oophoritis due to C. fetus subspecies fetus is very rare. To our knowledge, this case is the second case reported in Japan.