BACKGROUND The prevalence of nonmedical use of prescription opioids among American teenagers is staggering. Reducing the quantity of postoperative opioid prescriptions can help address this epidemic by decreasing the availability of opioids. As the fourth most common opioid prescribers, orthopaedic surgeons are primed to lead efforts to reverse this crisis. The purpose of this study was to determine patient factors associated with filling opioid prescriptions after pediatric orthopaedic surgery and to recommend potential methods to limit excess opioid prescriptions. METHODS This retrospective cohort study included 1413 patients who were prescribed opioids upon discharge after an orthopaedic surgical procedure at a single urban children's hospital from 2017 to 2018. The state's Prescription Drug Monitoring Program was used to determine which patients filled their opioid prescriptions. Comparisons of demographic, clinical, and surgical factors were made between patients that filled their opioid prescription upon discharge and those that did not. Statistical analysis included λ2, Mann-Whitney U, and binary logistic regression for significant factors from bivariate analysis. RESULTS Nine percent (n=127) of patients did not fill their opioid prescriptions after discharge. Those who filled and did not fill prescriptions were similar in terms of sex, ethnicity, race, insurance type, and age at surgery (P>0.05). Patients who did not fill their opioid prescriptions received significantly fewer opioids during their postoperative hospital course (5.3 vs. 7.7 mg oxycodone, P=0.01). Not receiving oral oxycodone during postoperative hospitalization (odds ratio=2.16, 95% confidence interval: 1.49-3.14) and undergoing upper extremity surgery (odds ratio=2.00, 95% confidence interval: 1.37-2.91) were independently associated with not filling opioid prescriptions after surgery in the multivariate analysis. CONCLUSIONS This study identified a subset of pediatric orthopaedic surgery patients who were prescribed opioids upon discharge but did not fill those prescriptions. Factors that increased the likelihood that patients did not fill their prescriptions upon discharge included fewer postoperative hospital course opioids, no oral oxycodone, and surgery on the upper extremity. Future studies must be performed to help decrease the number of opioids prescribed unnecessarily. METHODS Level III-prognostic cohort study.