Purpose <p>This study aimed to evaluate the clinical outcomes, failure rates, and complications associated with a second revision anterior cruciate ligament reconstruction using an Achilles tendon allograft in a mono-loop fashion, which allows simultaneous reconstruction of the anterior cruciate ligament and the anterolateral ligament. The hypothesis was that this combined technique is safe and leads to satisfactory clinical outcomes at mid-term follow-up.</p> Methods <p>A retrospective analysis was conducted on 20 patients who underwent a second revision ACL reconstruction between January 2018 and December 2022. All patients received an Achilles tendon allograft with a bone plug, used in a mono-loop technique to reconstruct both ACL and ALL. Exclusion criteria included multi-ligament injuries, posterior tibial slope &gt; 12°, or follow-up shorter than 24&#xa0;months. Clinical evaluation included pre- and postoperative scores: Tegner, subjective IKDC, Lysholm, and KOOS, as well as physical examination and Rolimeter testing. Mean follow-up was 32.2&#xa0;months.</p> Results <p>The mean patient age was 36.8 ± 6.3&#xa0;years. All clinical scores improved postoperatively: Tegner (from 64.3 to 87), subjective IKDC (55.1 to 64.4), Lysholm (58.2 to 76.9), and KOOS (59.7 to 70.1). Anteroposterior laxity decreased from 7.2 ± 2.1&#xa0;mm preoperatively to 1.2 ± 1.3&#xa0;mm postoperatively. A total of 55% of patients returned to their desired sports level, 25% to a lower level, and only one patient (5%) did not return owing to residual laxity. No postoperative complications or re-revisions were reported.</p> Conclusions <p>The mono-loop technique for simultaneous ACL and ALL reconstruction using an Achilles tendon allograft during a second revision procedure is safe and effective. It results in satisfactory mid-term outcomes, low failure rates, and no significant complications, providing a viable single-stage alternative for complex revision cases.</p> Study design <p>Cohort study; Level of evidence, 3.</p>