Septic arthritis of the hip joint after radiotherapy is a rare complication with distinctive features. It is difficult to recognize this complication because of its late onset and lack of significant fever. We describe three cases of patients with septic arthritis in the hip joint who had a history of radiotherapy in the pelvic region. Our patients developed septic arthritis 1, 2, and 3 years after radiotherapy and these occurrence intervals were relatively shorter when compared to previous literature. Hip joint destruction was noted in all cases. Resection of the femoral head was required to control the infection in two cases. Careful attention is requested to detect septic arthritis when patient experiences pain in joint where underwent radiotherapy. For this case, prompt laboratory study, radiological evaluation, and joint fluid aspiration and culture are required. If there is evidence of infection in these results, a proper and immediate treatment must be started.