Purpose <p>Pharmaceutical opioids significantly contribute to overdose deaths in Norway. This study investigated the prevalence of prescriptions and examined characteristics of those with filled prescriptions, comparing them to individuals without prescriptions.</p> Methods <p>This cohort study encompassed overdose deaths from 1.1.2005 to 31.12.2021, using toxicology and data linkage from nationwide health registries. Approximately 90% of Norwegian forensic autopsy cases were linked to the Norwegian Cause of Death Registry and the Norwegian Prescribed Drug Registry. The study included cases with overdose as cause of death, as defined by the European Union Drugs Agency (EUDA), along with benzodiazepine- and GHB-induced deaths (<i>N</i> = 3764). Detection and filled prescription of oxycodone, codeine, buprenorphine, methadone, tramadol, and fentanyl were studied.</p> Results <p>Fentanyl had the lowest proportion of filled prescriptions prior to death (27%), whereas codeine had the highest (67%). Buprenorphine and methadone, primary medications used in opioid agonist treatment (OAT) in Norway, showed low rates of filled prescriptions (33% and 29%, respectively). Women and older adults exhibited a higher prevalence of filled prescriptions compared to men and younger individuals. More than half of the individuals with prescribed opioids also had benzodiazepines prescribed and/or in their blood prior to death.</p> Conclusion <p>A substantial proportion of the deceased had filled prescriptions for opioids, indicating that medical treatment might be a crucial source for these substances in overdose deaths. Additionally, poly-drug use was common, especially opioids and benzodiazepines, highlighting the need for prescribers to be cautious.</p>