Purpose Hamstring tendon grafts are a popular choice for anterior cruciate ligament (ACL) reconstruction. Typical morbidity reported after hamstring tendon harvest is muscle weakness in flexion, and whilst still a matter for debate, this morbidity may be greater if the gracilis tendon is harvested in addition to the semitendinosus. This study sought to comprehensively compare the outcome of ACL reconstructions in which the semitendinosus was harvested alone (ST group) or with the gracilis (ST/G group). Methods Twenty patients (ten ST, ten ST/G) were assessed with a variety of measures that included subjective scores, function, strength and tibial rotation as measured by gait analysis during a pivoting task. Results Results showed that the graft diameter was significantly larger in the ST group, but there were no other differences between the groups for any other outcome measure. Conclusion Harvesting the gracilis in addition to semitendinosus does not appear to affect either the outcome or graft-related morbidity after hamstring ACL reconstruction.