BACKGROUND Anterior talofibular ligament (ATFL) is the most easily injured or even broken of ankle sprain. Patients who fail to receive conservative treatment, resulting in persistent ankle swelling, painful and functional decline that it is so-called chronic lateral ankle instability (CLAI). It makes sense to investigate all-inside arthroscopic reconstruction of ATFL with InternalBrace™ for CLAI. MATERIAL AND METHODS We included 108 patients who underwent all-inside arthroscopic ATFL reconstruction with InternalBrace™ for CLAI from January 2018 to April 2020 through a retrospective study. Patients age ranged from 19 to 58 years (mean 35.6±8.7 years). Several elements are used to evaluate the clinical consequences of ankle function, including the American Orthopedic Foot and Ankle Society (AOFAS), Japanese Society for Surgery of the Foot Ankle-Hindfoot (JSSF), Kofoed, Tegner scores and complications, and the tilt angle of talus (TT) and the anterior displacement of talus (ADT) with stressing radiographs were taken to measure in follow-ups. RESULTS All 108 patients had all-inside arthroscopic procedures performed smoothly without serious complications. During the follow-up period (26.7±2.6 months on average), no recurrence of ankle instability and other serious complications happened. The AOFAS, JSSF, Kofoed, and Tegner scores significantly increased as time went by postoperatively, which proved statistically significant (P<0.01). Regarding stress-radiographic measurements, TT significantly decreased from (9.5±1.1)° preoperatively to (2.6±0.6)° at the latest follow-up (P<0.01), while ADT significantly decreased from (9.5±1.0) mm preoperatively to (2.6±0.6) mm at the latest examination (P<0.01). CONCLUSIONS All-inside arthroscopic ATFL reconstruction with the InternalBrace™ for CLAI is beneficial for ankle stability, allowing earlier return to activities.