A 67-year-old man with a persistent high fever was diagnosed to have an infective aneurysm in his left internal iliac artery. A blood culture detected a gram-negative spiral rod that was first identified as Campylobacter fetus subsp. venerealis based on a matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS) analysis. However, the strain was finally confirmed to be Campylobacter fetus subsp. fetus based on a genetic analysis. The infection was successfully treated with emergency resection of the aneurysm, followed by 4 weeks of antibiotic therapy. Involvement of the peripheral artery is uncommon in cases of C. fetus-infective aneurysm. To figure out the epidemiology and pathogenicity of C. fetus infection, the accurate identification of the responsible organisms is essential.