We report a case of polyarticular septic arthritis with bilateral psoas abscesses. A 50-year-old woman was admitted with fever, multiple joint swelling and pain. She had a clinical history of acupuncture therapy for treatment of her chronic lower back pain two days before the appearance of her symptoms. Methicillin-sensitive Staphylococcus aureus was isolated from blood culture, knee joint fluids and psoas abscess. After a long course of antibiotics for 70 days together with drainage of the abscess, the condition completely resolved. The acupuncture is the probable cause of the infection, and this case report reveals the importance of asking about a clinical history of acupuncture treatment and of making repeated bacterial examinations in undiagnosed polyarthritis patients.