Background: The peroneus longus tendon (PLT) autograft is suggested as a promising alternative graft option for reconstructive procedures supported by a growing body of evidence indicating favorable results. However, concerns remain regarding long-term functional impairments of the foot and ankle after harvesting a full-thickness PLT.Purpose: To evaluate long-term donor site morbidity in patients who underwent anterior cruciate ligament reconstruction using a PLT autograft.Study Design: Case series; Level of evidence, 4.Methods: A retrospective review was performed to identify patients with harvested PLT autografts, and all eligible patients were invited to participate in a clinical examination at the hospital. To evaluate their range of motion, all included patients underwent a physical examination. Clinical outcomes were measured using the American Orthopaedic Foot and Ankle Society (AOFAS) score and the Activities of Daily Living and Sports subscales of the Foot and Ankle Ability Measure (FAAM-ADL and FAAM-S). To evaluate foot and ankle structural changes, the intermetatarsal angle (IMA), hallux valgus angle (HVA), arc height index (AHI), lateral talo-first metatarsal angle (LTFMA), calcaneal pitch angle (CPA), and metatarsal angle (MA) were measured in the PLT harvested side and the contralateral side.Results: A total of 26 patients who were available for the final follow-up were included in this study. The mean age of the patients at the final follow-up was 45.7 +/- 9.5 years. The mean follow-up time was 19.5 +/- 3.4 years. AOFAS scores were excellent in 92.3% of patients (n = 24) and good in 7.7% (n = 2). The mean FAAM-ADL score was 99.6 +/- 1.86. The mean FAAM-S score was 98.1 +/- 5.94. No statistically significant differences were observed between the PLT harvested side and the contralateral side for any of the measured parameters-including the IMA, HVA, AHI, LTFMA, CPA, and MA.Conclusion: This study demonstrated good to excellent long-term patient-reported outcomes and negligible radiographic changes after harvesting the full thickness PLT compared with the contralateral side. These long-term data strongly support PLT harvesting as an alternative graft choice and suggest that this method does not alter the natural history of foot and ankle structures.