Background: Femoral nerve block (FNB) is a popular technique for reducing postoperative pain in patients with anterior cruciate ligament reconstruction (ACLR), but it is also linked to a number of adverse effects, such as quadriceps weakness, antalgic ambulation, and increased fall risk. Adductor canal block (ACB) has been offered as a motor nerve–sparing alternative to FNB. Purpose: To evaluate available literature that compares the effects of ACB and FNB on functional outcomes after arthroscopic ACLR. Study Design: Systematic review. Methods: Following the 2009 PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines, a search of PubMed (Ovid), CINAHL, Scopus, Cochrane, and Google Scholar databases was conducted. Search terms were designed to capture studies comparing the effects of ACB and FNB in patients undergoing arthroscopic ACLR. Data were evaluated regarding study and patient characteristics, functional measures, opioid consumption, pain scores, and complications. Results: Eight randomized controlled trials (N = 655 patients) comparing the efficacy of ACB versus FNB in arthroscopic ACLR were included. The heterogeneity of outcome measures precluded meta-analysis. Seven studies reported functional measures, which included isokinetic strength, straight-leg raise, and other various measures. Follow-up periods varied between 1 hour and 6 months. In 3 trials, ACB was found to preserve quadriceps strength as measured using straight-leg raise for the first 12 to 24 hours after surgery, while 3 other trials found no difference between the groups. No differences were reported in isokinetic strength at 6 months. In other functional measures, ACB either outperformed or was equivalent to FNB. The majority of studies reporting opioid consumption, pain scores, and complications found no differences between the blocks. Conclusion: This systematic review suggests that when compared with FNB, ACB preserves quadriceps function in the early postoperative period after ACLR while providing a similar level of analgesia. Limitations of this study include the use of various functional measures and limited long-term follow-up. More research evaluating long-term functional outcomes with standardized measures is needed to draw adequate conclusions regarding the effects of ACB and FNB on function after ACLR.