Abstract Background Shockwave was shown to enhance the healing of anterior cruciate ligament (ACL) reconstruction in rabbits. This study evaluated the effect of extracorporeal shockwave therapy (ESWT) on ACL reconstruction in human subjects. We hypothesized that ESWT may improve human ACL reconstruction. Methods Fifty-three patients were randomized into two groups with 26 patients in ESWT group and 27 patients in control group. The ESWT group underwent single-bundle hamstring autograft ACL reconstruction and received ESWT immediately after surgery. The control group underwent ACL surgery without ESWT. Both groups received the same rehabilitation postoperatively. The evaluations included Lysholm score, IKDC score and KT-1000, radiograph, bone mineral density, and magnetic resonance imaging. Results ESWT group showed significantly better Lysholm score than control group at 1 and 2 y postoperatively (P < 0.001 and 0.001, respectively). No significant difference was noted in IKDC score between the two groups (P = 0.080 and 0.076, respectively). The KT-1000 values were significantly better in ESWT group than control group at 2 y postoperatively (P = 0.027). The tibia tunnel on X-ray was significantly smaller in ESWT group compared with control group at 2 y (P = 0.018). The bone mineral density values showed no discernable difference between the two groups at 6 mo and 2 y (P = 0.522 and 0.984, respectively). On magnetic resonance imaging, ESWT group showed significant decrease in tibia tunnel enlargement at 6 mo and 2 y compared with the control group (P = 0.024 and <0.001, respectively). Conclusions ESWT significantly improves the subjective Lysholm score and decreases the middle 1/3 tibia tunnel enlargement after single hamstring autograft ACL reconstruction.