Background: Young patients undergoing anterior cruciate ligament (ACL) reconstruction (ACLR) are at a particularly high risk of graft ruptures compared with adults. Recent studies have demonstrated significant reductions in ACL graft rupture rates in high-risk adult populations when a lateral extra-articular procedure is performed, but comparative studies in pediatric and adolescent populations are currently lacking in the literature. Purpose/Hypothesis: The purpose of this study was to compare the clinical outcomes of isolated ACLR versus combined ACLR and lateral extra-articular tenodesis (LET) when using the Arnold-Coker modification of the MacIntosh procedure in early adolescent patients. The hypothesis was that combined procedures would be associated with a significantly reduced risk of graft ruptures. Study Design: Cohort study; Level of evidence, 3. Methods: A retrospective analysis of consecutive early adolescent patients who underwent ACLR using a hamstring tendon autograft with or without the Arnold-Coker modification of the MacIntosh procedure was conducted. Patients with ≥1 additional risk factors for a graft rupture were offered LET in addition to ACLR (pivot-shift grade 2 or 3, high level of sporting activity defined as Tegner activity score ≥7, participation in pivoting sports, and Segond fractures). Clinical outcomes including graft rupture rates, patient-reported outcome measure scores (Knee injury and Osteoarthritis Outcome Score and subjective International Knee Documentation Committee), knee stability, return-to-sports rates, reoperation rates, and complications were assessed. Comparisons between variables were assessed with the chi-square or Fisher exact test for categorical variables and the Student or Wilcoxon test for quantitative variables. Multivariate analyses were undertaken to evaluate risk factors for a graft rupture. Results: A total of 111 patients with a mean follow-up of 43.8 ± 17.6 months (range, 24-89 months) were included in the study; 40 patients underwent isolated ACLR, and 71 underwent ACLR + LET. The addition of LET to ACLR was associated with a significantly lower graft rupture rate compared with isolated ACLR (0.0% vs 15.0%, respectively; odds ratio, 15.91 [95% CI, 1.81-139.44]; P = .012). It was also associated with significantly better knee stability (pivot-shift grade 3: 0.0% vs 11.4%, respectively; P = .021) (side-to-side anteroposterior laxity difference >5 mm: 0.0% vs 17.1%, respectively; P = .003) and Tegner activity scores (7 vs 6, respectively; P = .010). There were no significant differences between the groups regarding the Patient Acceptable Symptom State for the patient-reported outcome measures, nor for any of the other outcome measures evaluated, and no differences in the rate of non–graft rupture related reoperations or complications. The ACLR + LET group exceeded the minimal clinically important difference with respect to the Tegner activity scale. Conclusion: In a retrospective comparative cohort study of adolescents, combined ACLR and LET was associated with a significantly lower graft rupture rate and no difference in non–graft rupture related reoperations or complications compared with isolated ACLR.