Abstract The aim of this study was to identify the risk factors for free flap failure after head and neck reconstructive surgery. The data of 881 consecutive patients who underwent free flap surgery at the Department of Oral and Maxillofacial Surgery, Peking University School and Hospital of Stomatology, between January 2013 and November 2016, were reviewed retrospectively. All surgeries were performed by a single head and neck surgical team. Patient demographic and surgical data that may have an influence on free flap outcomes were recorded. The χ2 test and multivariate logistic regression analysis were used to identify relevant risk factors. In total, 881 free tissue transfer surgeries were included in this study. Free flap failure occurred in 26 of 881 flaps (2.9%). A history of irradiation (odds ratio 0.205, 95% confidence interval 0.07–0.56; P = 0.002) was a statistically significant risk factor for free flap failure. Age, diabetes mellitus, history of previous neck surgery to the anastomosis side, donor site, choice of recipient vein, use of a coupler device, and postoperative anticoagulation were not associated with free flap outcomes. Thus, it is concluded that when performing head and neck reconstructive surgery, special attention should be paid to patients who have previously undergone irradiation.