Purpose The purpose of this study is to evaluate the reasons why athletes do not return to play (RTP) following anterior cruciate ligament (ACL) reconstruction from a large single-centre database. Methods The institutional ACL registry was screened for patients that had undergone a primary ACLR and had RTP status reported at 24-month follow-up. The reasons that patients were unable to RTP at 24 months were evaluated. The ACL-Return to Sport Index (ACL-RSI) was evaluated at baseline and 24-month follow-up to evaluate psychological ability to RTP. Results At 2 years, 1140 patients returned to play, and 222 had not returned to play. The most common reasons athletes were unable to return was fear of reinjury (27.5%), lack of confidence in performance on return (19.4%) and external life factors (16.6%), i.e. work commitments and family reasons. Other reasons for athletes not returning to play were residual knee pain (10%) and subsequent injury (5%). The ACL-RSI score was significantly lower at diagnosis (40.3 vs. 49.3; p  = 0.003) and 2 years (41.8 vs. 78.7; p  < 0.0001) in athletes who did not return to play vs. those that did RTP. Conclusion The majority of patients that report they have not returned to play do so due to external life and psychological factors associated with their injury, including fear of reinjury and lack of confidence in performance. A small minority of patients were unable to return due to residual knee symptoms or reinjury. Pre-operative psychological assessment and intervention may identify those less likely to RTP and provide an opportunity for targeted interventions to further improve RTP outcomes. Level of evidence III.