Background Osteoradionecrosis of the jaw is a severe complication of radiotherapy in head and neck cancer patients. If conservative treatment and surgical debridement have been unsuccessful, the preferred treatment for symptomatic mandibular osteoradionecrosis (mORN) is radical surgery and subsequent reconstruction with a free vascularized flap. This study aims to assess the outcomes of free vascularized flap reconstruction in mORN. Methods A retrospective study was conducted on all patients who underwent a free vascularized flap reconstruction for mORN between 1995 and 2021 in Amsterdam UMC – VUmc, The Netherlands. Results In our cohort study, three of the twenty-eight flap reconstructions failed (10.7%). No recurrences of mORN were observed during a mean follow-up of 8 years. Conclusions The success rate of free vascularized flap reconstruction for mORN is high. The fibula is the preferred free flap for mandibular reconstruction in mORN cases. However, this type of surgery is at risk for complications and patients need to be informed that these complications may require surgical re-intervention. Level of evidence: Level IV, Therapeutic; Risk/Prognostic.