Prevotella bivia is an obligatory anaerobic, gram-negative rod, which often produces a detectable beta-lactamase. To date, there has been only 3 descriptions of septic arthritis secondary to this microorganism in a patients pre-existing sever joint disease like rheumatoid arthritis and osteoarthritis or after joint prosthesis. We are reporting the first case of septic arthritis due to Prevotella bivia in a patient with no pre-existing joint symptoms.