Little is known about private-market opioid prescribing and how Australian opioid policies impact prescribing across public and private markets in Australia. We aimed to investigate publicly subsidised and private-market opioid prescribing from 2013 to 2018. We used prescribing records from MedicineInsight, an Australian primary care database, to examine trends in prescriptions for non-injectable opioid formulations from October 2013 to September 2018. We examined annual opioid prescribing trends overall, by opioid agent, and by market (public and private). We further examined patterns of fentanyl patch prescribing focusing on co-prescribed medicines and use in opioid-naïve patients. Opioids accounted for 8% of all prescriptions over the study period and 468 893 patients were prescribed at least one opioid of interest. Prescribing rates for oxycodone/naloxone and tapentadol increased, whereas those for fentanyl patches, morphine and single-agent oxycodone decreased over the study period. Private-market prescribing rates of codeine (schedule 4) increased notably following its up-scheduling to prescription-only status. Among patients prescribed fentanyl patches, 29% were potentially opioid-naïve and 49% were prescribed another opioid on the same day. The private-medicines market is a small but growing component of opioid use in Australia and one way in which prescribers and patients can avoid access restrictions in the public market for these medicines. Although fentanyl patch prescribing declined, there is room for improvement in prescribing fentanyl patches among opioid-naïve patients, and co-prescribing of fentanyl patches with other sedatives.