One hundred and twenty patients with chronic ACL tears who were undergoing ACL reconstruction (ACLR) and were deemed to be at a high risk of clinical failure were randomized to receive ACLR and anterolateral structure augmentation (ALSA) (n=63) or ALCR alone (n=57). The primary outcome of interest was the rate of clinical failure. Clinical failure was defined by physical examination (Lachman test, anterior drawer test grade 2 of 3, a side-to-side difference of >5 mm on a KT-1000 arthrometer [MEDmetric], a pivot-shift test grade of 2 of 3 or a persistent pivot-shift test grade of 1 detected at 2 visits) or graft rerupture as confirmed via imaging or arthroscopic examination. Secondary outcomes included patient-reported outcomes and return to play. The ACLR + ALSA group had significantly lower rates of clinical failure than the ACLR alone group. There was no differences in patient reported outcomes as measured by the Lysholm score, subject International Knee Documentation Committee (IKDC) score, Tegner score and Marx activity scale score. There was no difference in the overall return to play rates but patients in the ACLR + ALSA group had significantly higher rates of return to preinjury level and return to competitive sport.