INTRODUCTION: Ankle sprains can lead to chronic lateral ankle instability (CLAI) in 10-50% of cases. While the anterior talofibular ligament (ATFL) is traditionally considered the primary structure affected, recent studies indicate a high incidence of combined injuries to the ATFL and the calcaneofibular ligament (CFL). Given the importance of the CFL, this study aims to evaluate the biomechanical efficacy of double tendon graft reconstruction of the ATFL and CFL in cases of CLAI. MATERIALS AND METHODS: This biomechanical study on cadaveric ankles compares two techniques: anatomical reconstruction using a double graft for both the ATFL and CFL versus isolated anatomical reconstruction of the ATFL with a single graft. Stability was assessed using specific examination maneuvers (anterior drawer, forced varus, and pivot shift) with an arthrometer measuring angular displacement across three spatial planes (horizontal, coronal, and sagittal). Four models were analyzed: intact ankle, sectioning of the ATFL and CFL, double graft reconstruction of the ATFL and CFL, and single graft reconstruction of the ATFL. RESULTS: The results showed no significant differences between the double graft reconstruction and the intact ankle. Comparing the double graft with the single graft reconstruction revealed statistically significant differences, favoring the double graft for greater angular stability in the coronal plane during forced varus and external rotation maneuvers. CONCLUSIONS: Double graft reconstruction of the ATFL and CFL provides greater angular stability compared to isolated ATFL reconstruction, demonstrating significant benefits in lateral and rotational stabilization of the ankle in CLAI cases.