Using administrative data and patient interviews, this study sought to estimate opioid-related adverse events in adults discharged from one Canadian hospital. Among patients who filled at least one opioid prescription in the 90 days following hospital discharge, approximately 16% experienced an opioid-related emergency department visit, hospital readmission, or death. Longer duration of use and higher daily dose were associated with increased risk of adverse events. Results from this study can inform policies and strategies to limit opioid prescription dose and duration.