Campylobacter fetus subsp. fetus causes systemic diseases including bacteremia and meningitis. However, it rarely causes bacterial pericarditis. We present a rare case of bacterial pericarditis caused by Campylobacter fetus subsp. fetus. A man in his 60s presented with a fever and dyspnea. Electrocardiography revealed ST segment elevation in all leads except augmented vector right (aVR), and contrast-enhanced computed tomography of the chest revealed a large pericardial effusion. Campylobacter fetus subsp. fetus, appearing as curved, gull-wing-shaped gram-negative rods on microscopy, was identified on blood culture. The patient was diagnosed with acute pericarditis caused by Campylobacter fetus subsp. fetus. Further, history-taking revealed that he had consumed undercooked mutton before the onset of his illness. He recovered after treatment with antibiotics (ceftriaxone, ampicillin, and amoxicillin) for four weeks. With a blood culture revealing gull-wing shaped gram-negative rods, and the patient's history including potential contact with animals or the consumption of raw or undercooked meat, Campylobacter fetus subsp. fetus infection should be suspected.