Background: To assess the clinical and functional outcomes of all-inside arthroscopic anatomical repair of anterior talofibular ligament (ATFL) for management of chronic lateral ankle instability (CLAI) in a considerable number of patients during medium-term follow-up. Methods: A retrospective analytic study was performed on 100 patients with CLAI who presented between August 2015 and July 2020 (average age: 32.9 years; range: 16-54 years). All-inside arthroscopic ATFL direct repair was performed in all patients through 2 portals only with fixation using 2 knotless anchors. Associated intraarticular lesions were treated in the same procedure. Outcomes were assessed with pre- and postoperative visual analog scale (VAS), the ankle-hindfoot score of the American Orthopaedic Foot & Ankle Society (AOFAS), and the Karlsson Ankle Functional Score (KAFS). Results: All patients were followed for 24-48 months. At the final follow-up, ankle pain had improved significantly. Both the ankle anterior drawer test and the ankle varus stress tests were negative. There was no loss of ankle range of motion compared with preoperative measures, and all patients returned to normal gait. The mean VAS score decreased to 0.39 ± 0.63, the AOFAS score increased to 95.17 ± 4.7, and the KAFS score increased to 95 ± 4.07. All the follow-up indexes significantly improved compared to those before surgery. Conclusion: At minimum 24-month follow-up, the all-inside arthroscopic ATFL repair used to treat CLAI was found to restore ankle stability and yield good clinical outcomes with a relatively low complication rate. Level of Evidence: Level III, retrospective cohort study.