To determine whether the psychological characteristics of athletes who have undergone an anterior cruciate ligament (ACL) reconstruction change during rehabilitation are related to returning to competitive sport.Prospective longitudinal study.87 athletes completed the Emotional Response of Athletes to Injury Questionnaire (ERAIQ) and the ACL Return to Sport after Injury scale (ACL-RSI) at 3, 6 and 12 months following ACL reconstruction surgery. Physical outcome measures were also taken at each time point.At 12 months 44 (51%) participants had returned to competitive sport and 43 (49%) participants had not returned. There were no differences in physical recovery or scores on the ERAIQ between the two groups. Participants who had returned to competitive sport at 12 months, however, scored significantly higher on the ACL-RSI scale (reflecting a more positive psychological response about sport participation) at both 6 and 12 months than participants who had not returned to competitive sport.During rehabilitation there are significant psychological differences regarding sport resumption between athletes who do, and do not, resume competitive sport 12 months following ACL reconstruction. These differences occur as early as 6 months postoperatively and highlight the importance of addressing all aspects of an athlete's recovery in order to help facilitate the athlete returning to sport.