BACKGROUND: The aim of this prospective randomized clinical study was to compare the clinical and second-look arthroscopic outcomes of early weight-bearing and delayed weight-bearing rehabilitation protocols following anterior cruciate ligament (ACL) reconstruction with hamstring tendons. METHODS: This prospective study involved 90 patients who underwent ACL reconstruction with hamstring tendons. The patients were randomly assigned to either perform weight-bearing exercises at three weeks postoperatively (group A) or at one week postoperatively (group B). Evaluation of the patients was conducted at 3, 6, and 12 months postoperatively, focusing on knee range of motion, thigh circumference, and knee function assessed using the International Knee Documentation Committee (IKDC) form and Lysholm knee score. Graft evaluation was performed based on tension, tear, and synovial coverage via second-look arthroscopy at least one year after reconstruction. RESULTS: Group B exhibited significantly greater knee extension and fiexion an gles at 3 and 6 months compared to group A. IKDC and Lysholm scores were significantly higher in group B at 3 and 6 months. Additionally, the difference in thigh circumference between groups A and B was smaller at all evaluation periods, indicating less muscle atrophy in group B. Furthermore, there was no significant difference in synovial coverage, graft tear, or tension between the two groups based on second-look arthroscopy findings. CONCLUSIONS: This study demonstrates that an early weight-bearing protocol leads to faster recovery of knee joint function and muscle strength, facilitating a quicker return to sports activities. Additionally, there was no significant difference in graft morphology observed at second-look arthroscopy between the two groups at one year postoperative. Therefore, clinicians are encouraged to develop suitable early weight-bearing rehabilitation protocols for patients who have undergone ACL surgery.