Context:Anterior cruciate ligament (ACL) reconstruction in older patients is a controversial topic among orthopaedic surgeons.Objective:To determine the outcomes, failure, and morbidity associated with ACL reconstruction in patients older than 40 years and to compare it with nonoperative treatment as well as results of ACL reconstruction in a younger patient population.Data Sources:A systematic review of the literature from 1970 to 2015 was conducted utilizing MEDLINE, CINAHL, and the Cochrane Central Register databases using PRISMA guidelines.Study Selection:Inclusion criteria were studies with longer than 2-year follow-up of primary ACL reconstruction and minimum age of patients older than 40 years, inclusive of any graft type or source and of any concomitant meniscal pathology.Study Design:Systematic review.Level of Evidence:Level 4.Data Extraction:Two independent reviewers collected demographic, preoperative, intraoperative, and postoperative data.Results:Twelve studies with a total of 452 patients were included. The mean patient age was 47.8 years (range, 40-66 years) with a mean follow-up of 53.3 months (minimum, 24 months). Lysholm scores improved from 53.9 to 90.5 in the 11 operative studies. The only nonoperative study reported a mean Lysholm score of 82 after rehabilitation. International Knee Documentation Committee (IKDC) scores of A or B were found in 81%. Tegner activity scores averaged 4.7 preinjury, fell to 2.9 preoperatively, and returned to 4.7 postoperatively. The reported failure rate was 2.3%. There were few complications, and failure rate was similar in younger patients.Conclusion:The data confirm that ACL reconstruction can be recommended to patients older than 40 years who wish to maintain an active lifestyle or have symptomatic instability with daily activities. Patient-based outcomes scores were better in the operative studies compared with the single nonoperative study in this patient population.