Purpose: Radiological examinations including X-ray and CT play a critical role in the assessment and treatment of trauma patients. The ionizing radiation used is known to be carcinogenic. However, little is known about the total radiation exposure in trauma patients. The objective of this study was to accurately estimate radiation exposure of patients with severe pelvic ring fractures. Methods: In this retrospective dynamic cohort study, adult patients with partially stable and unstable pelvic ring fractures were included. For each patient, data concerning demography and injury characteristics were collected. Subsequently, the total effective radiation dose due to all trauma-related X-rays and CT scans during initial assessment, treatment and follow-up was calculated using Monte Carlo software. Results: A total of 114 patients were included. The median total effective dose was 49.7 millisievert (mSv). 57 patients (50.0%) received more than 50 mSv and 13 patients (11.4%) received more than 100 mSv. 62.4% of the total effective dose was received within the 24 h after admission. The median total effective dose for survivors (n = 95) was 52.0 mSv. Polytrauma patients received a significantly higher total effective dose than non-polytrauma patients. Conclusions: This study showed that a substantial number of patients with partially stable and unstable pelvic ring fractures have an increased cancer risk due to trauma-related medical imaging. Physicians should be aware of the amount of radiation their patients are exposed to, and minimize imaging related increase of cancer risks during initial assessment, treatment and follow-up.