Osteomyelitis is an inflammatory disease of the bone that usually begins as an infection of the medullary cavity, rapidly involves the haversian system, and quickly extends to the periosteum of the area. It develops in the femur bone after a chronic infection or for a variety of other reasons such as trauma to the femur. When antimicrobial agents or drainage prove unsuccessful, acute osteomyelitis may become chronic. Conventional radiography, culture, bone biopsy, computed tomography (CT), and magnetic resonance imaging (MRI) are used for its diagnosis. In this report, we present a case that was initially diagnosed as osteoid osteoma and finally diagnosed with chronic osteomyelitis, which was successfully treated with surgery and antibiotic treatment.