|Purpose: To evaluate the restoration of the flexor power and the correlation between the flexor power and functional performance tests (FPTs) after anterior cruciate ligament (ACL) reconstruction with hamstring autograft. Materials and Methods: Twenty-three men, who underwent ACL reconstruction with hamstring autograft, were evaluated using Lysholm, Subjective IKDC, Tegner activity score, isokinetic flexion and hyperflexion power test, and the FPTs at 1 and 2-year follow-up. We analyzed the mean change from 1 to 2 year and the correlation between both the flexion and hyperflexion power deficit with the FPTs at each follow-up. Results: Mean age of the patients was 30.9 years (range, 19 to 44). Tegner activity score was significantly increased from 5.7 to 6.3 (p=.010). Hyperflexion power of the involved knee deficits significantly decreased at 2 year follow-up compared with 1 year (p<.001). There was a correlation between the flexor power deficit and the co-contraction, carioca, and involved one-legged hop test at each follow-up. However, no significant correlations were revealed between the hyperflexion power deficit and the FPTs. Conclusions: Hyperflexion power deficit after ACL reconstruction with the hamstring autograft decreased at 2 year follow-up compared to 1 year and does not affect the results of the FPTs.