In the first two weeks after their release from prison, people are at greater risk than usual of fatal opioid overdose. They are also at greater risk of non-fatal opioid overdose, which is associated with considerable morbidity. An analysis of linked Queensland ambulance data (non-fatal opioid overdose-related ambulance contacts defined as those reporting improved Glasgow Coma Scale [GCS] scores or case notes describing clinical improvement after naloxone administration) estimated that the crude incidence rate of non-fatal opioid overdose among people released from prison was 4.5 (95% confidence interval [CI], 2.8–7.2) cases per 1000 person-years. However, the study included people who reported never having injected drugs, and thereby probably underestimated non-fatal opioid overdose incidence among those at greatest risk: people who had injected drugs prior to their imprisonment.