BACKGROUND:There is limited information about patient expectations regarding return to sport after anterior cruciate ligament reconstruction (ACLR). While it has generally been assumed that patients expect to return, it has also been acknowledged that expectations may change after surgery. PURPOSE:To investigate return-to-sport expectations before and after ACLR and determine factors associated with changed expectations. STUDY DESIGN:Cohort study; Level of evidence, 2. METHODS:The study sample consisted of 675 eligible patients (437 male, 238 female). Return-to-sport expectations were recorded preoperatively. Primary ACLR was performed in 595 patients (of whom 81 had a prior contralateral ACLR) and revision ACLR in 80 patients. At 12 months after surgery, the return to preinjury sport status was assessed along with patients' current sport expectations. The proportion of patients who expected to return to their preinjury level of sport was determined along with actual return rates. Logistic regression was performed to determine the factors associated with the decision to cease sport participation in patients who had expected to be able to return to their preinjury level of sport. RESULTS:Overall, 84% of patients expected to be able to return to their preinjury level of sport. Expectations were higher for patients about to undergo their first ACLR, with 88% expecting to return, than for those about to undergo revision surgery or second primary ACLR (63% and 80% expected to return, respectively; P < .001 and P = .08, respectively). At 12 months after surgery, 24% of patients who expected to return to their preinjury level of sport had actually returned, and 15% of all patients had already decided to give up sport. In the regression models, being female ( P = .02) and having undergone previous ACLR ( P < .0001) were factors significantly associated with the decision to give up sport participation. CONCLUSION:Patients had high expectations for returning to their preinjury level of sport at the time of undergoing initial ACLR. Expectations were lower for those who had undergone previous ACLR. Female patients and patients who had undergone previous ACLR were more likely to change their expectations and cease sport participation. These data can be used to provide patients with realistic return-to-sport expectations in the first postoperative year and highlight the challenge for patients who aim to return from multiple ACL injuries.