AIMS:A sustained-release formulation (SRF) of tapentadol has been marketed in Australia since February 2013. This study examined tapentadol SRF extra-medical use, attractiveness for extra-medical use, and associated harms in Australia. METHODS:This post-marketing study comprises analyses of Australian community sales data (2011-2017) for eleven pharmaceutical opioids (prescription and over-the-counter codeine disaggregated); calls to three poisons information centres (covering five of the eight jurisdictions in Australia) related to pharmaceutical opioids and coded by the centres as 'misuse' or 'abuse' (2011-2017); and interviews with people who inject drugs (n = 888) recruited as part of the Illicit Drug Reporting System (IDRS) from all Australian capital cities (2017). RESULTS:Population-level availability of tapentadol SRF increased from market launch, comprising the sixth largest market share of all opioid unit sales, and third greatest share in oral morphine equivalent milligrams sold, in December 2017. Lifetime tapentadol SRF use among the IDRS sample (n = 888) was low (1.5%; 95%CI 0.9-2.5), with few reporting past-6 month non-prescribed use or injection. Non-fatal overdose following tapentadol use was self-reported by less than 1% (95%CI 0.1-0.8). Between 2013-2017, 1.1% (n = 25) of pharmaceutical opioid 'misuse/abuse' calls were related to tapentadol, and predominantly the SRF. CONCLUSIONS:Increasing utilisation of tapentadol sustained-release formulation was observed, along with indications of extra-medical use and harms associated with use, although on a smaller scale relative to other opioids. These findings need to be interpreted in the context of the low level of exposure to tapentadol sustained-release formulation among the sentinel population of people who inject drugs.