Introduction: Anterior cruciate ligament (ACL) injury is the common knee injury consequent to contact sports. There are different techniques recommended for the ACL reconstruction, with different graft materials. The aim of this study is to evaluate the functional outcome of arthroscopic single bundle ACL reconstruction using hamstring tendon graft in ACL deficient knees in adults. Materials and Methods: Between 2014 and 2017, a prospective study was conducted in Thanjavur Medical College on 10 ACL deficient patients. All patients were evaluated preoperatively using the Lysholm and Gillquist score and IKDC – 2000 score. All patients underwent arthroscopic single bundle ACL reconstruction with hamstring tendon graft, which was fixed with an endo-button CL fixation system on the femoral side and an interference screw on tibial side. They were advised a regular rehabilitation protocol. All patients were evaluated post-operatively at 6 weeks, 3 months, 6 months, and a year by same assessment scores. Results: Ten patients were available for follow up for a period of 6 months to 2 years. The mean follow-up period was 10.5 months. When compared with their respective pre-operative knee assessment scores, it was found that a definite improvement was there in their knee function. The results were good to excellent in 80% patients, fair in 10%, and poor in 10% cases. Conclusion: For young active adults, single bundle reconstruction by arthroscopic methods gives acceptable results. The problems which are faced post-operatively can be again settled arthroscopically. A long-term follow-up of these cases is a must to analyze if there is degeneration that happened in the time between injury and ligament reconstruction. Keywords: ACL reconstruction, hamstring graft, lysholm and gillquist score.