BACKGROUND The aim of this study is to report our institution's experience regarding the application of allogeneic tendons for the reconstruction of malunited lateral malleolar avulsion fractures with chronic lateral ankle instability. METHODS This retrospective study included 34 (34 ankles) patients surgically treated for malunited lateral malleolar avulsion fractures with chronic lateral ankle instability from January 2016 to December 2019. All patients underwent allogeneic tendon reconstruction. The pre- and postoperative American Orthopaedic Foot and Ankle Society (AOFAS) scores、Karlsson Ankle Functional Scores (KAFS) and visual analogue scale (VAS) scores were used to evaluate the functional recovery of the ankle joint. The final follow-up, based on radiographic assessment, including talar tilt and anterior talar translation, was performed to evaluate the stability of the postoperative ankle joints. RESULTS Thirty-two patients (32 ankles) returned for final clinical and radiologic follow-up at an average of 29 (range 24-35) months and 2 patients (2 ankles) were lost to follow-up. The preoperative talus inclination angle (13.6 ± 1.9°) and anterior displacement (9.6 ± 2.8 mm) were re-examined under X-ray and found to be reduced to 3.4 ± 1.2° and 3.8 ± 1.1 mm, respectively (p＜0.01). The AOFAS scores increased from 58.5 ± 4.0 to 90.9 ± 3.8 and the Karlsson scores improved from 52.2 ± 3.6 to 89.8 ± 4.5, which was obviously better and the difference was statistically significant (P < 0.01). The VAS scores were significantly reduced from a preoperative mean of 6.8 ± 1.0 to 2.8 ± 0.9 postoperatively (p＜0.01). CONCLUSIONS In this population and with this follow-up, the application of allogeneic tendons to treat malunited lateral malleolar avulsion fractures combined with chronic lateral ankle instability appeared safe and effective.