OBJECTIVES: This study clarified the incidence of and identified the risk factors for post-radiation pelvic insufficiency fractures (PIFs) in women who received postoperative definitive or adjuvant radiotherapy (RT) for cervical cancer. PATIENTS AND METHODS: The medical records and data of imaging studies, including computed tomography scan and magnetic resonance imaging, of women with cervical cancer who received external-beam RT for the entire pelvic area between January 2003 and December 2012 at our institution were reviewed. RESULTS: A total of 533 patients with histologically diagnosed cervical cancer who received RT (298: definitive RT, 235: adjuvant RT) were included in this study. Eighty-four patients (15.8%) developed PIF in the irradiated field. Median age at onset of PIF was 72.5years (range: 54-95years), and 82 of them (98%) were postmenopausal women. Sixty-nine patients (80%) developed PIF within 3years from the completion of RT. The median time for the development of PIF was 14months (range: 1-81months). The most commonly involved fracture site was the sacral bone. Postmenopausal state, coexistence of rheumatoid arthritis, and high-dose-rate intracavitary brachytherapy (HDR-ICBT) use were significant predisposing factors for the development of PIF, according to multivariate analysis. CONCLUSIONS: The incidence rate of PIF among patients who received RT for locally advanced cervical cancer was 15.8%. The principal predisposing factors for post-radiation PIF were postmenopausal state, rheumatoid arthritis, and HDR-ICBT use. Active interventions, including bone density screening followed by medication, should be considered during the early stage of RT for women with high-risk factors of PIF.