The present article documents a case of Fusobacterium sepsis with a transient anticardiolipin antibody increase in an otherwise healthy 24-year-old patient. He was presented to the emergency room with headache and fever. His temperature was 39.5°C, laboratory results revealed a white blood count of 15.2×10(3)/μl and C reactive protein 22.6 mg/dl. The patient was admitted. Chest X-ray showed the infiltrate in bilateral lower lung area. He received 400 mg of clarithromycin per day. His all symptoms did not change. On the 8(th) day in the hospital, the patient's antibiotics were switched to pazufloxacin. Chest and abdominal CT scan showed some irregular patchy nodules of around 1 cm in diameter in the bilateral lower lung fields and a round low density lesion 3 cm in diameter in the right upper segment (S8) in the liver. Blood culture revealed Fusobacterium necrophorum. On the 10(th) day, the antibacterial agent was changed from pazufloxacin to ampicillin sulbactam. On the 17(th) day, we added clindamycin. As a result his temperature gradually returned to normal. It is reported that the titer of anticardiolipin antibody increases in the sepsis patients caused by Fusobacterium necrophorum. As his symptoms disappeared, his titer of anticardiolipin antibody also decreased. So we considered he had a transient anticardiolipin titer increase.