BACKGROUND: Up to two-thirds of athletes may not return to their preinjury level of sport by 12 months after anterior cruciate ligament (ACL) reconstruction surgery, despite being physically recovered. This has led to questions about what other factors may influence return to sport. PURPOSE: To determine whether psychological factors predicted return to preinjury level of sport by 12 months after ACL reconstruction surgery. STUDY DESIGN: Case control study; Level of evidence, 3. METHODS: Recreational and competitive-level athletes seen at a private orthopaedic clinic with an ACL injury were consecutively recruited. The primary outcome was return to the preinjury level of sports participation. The psychological factors evaluated were psychological readiness to return to sport, fear of reinjury, mood, emotions, sport locus of control, and recovery expectations. Participants were followed up preoperatively and at 4 and 12 months postoperatively. RESULTS: In total, 187 athletes participated. At 12 months, 56 athletes (31%) had returned to their preinjury level of sports participation. Significant independent contributions to returning to the preinjury level by 12 months after surgery were made by psychological readiness to return to sport, fear of reinjury, sport locus of control, and the athlete's estimate of the number of months it would take to return to sport, as measured preoperatively (χ(2) 2 = 18.3, P < .001, classification accuracy = 70%) and at 4 months postoperatively (χ(2) 4 = 38.7, P < .001, classification accuracy = 86%). CONCLUSION: Psychological responses before surgery and in early recovery were associated with returning to preinjury level of sport at 12 months, suggesting that attention to psychological recovery in addition to physical recovery after ACL injury and reconstruction surgery may be warranted. Clinical screening for maladaptive psychological responses in athletes before and soon after surgery may help clinicians identify athletes at risk of not returning to their preinjury level of sport by 12 months.