BACKGROUND: This study aimed to investigate the prevalence of diversion and injection of methadone and buprenorphine among clients receiving opioid pharmacotherapy treatment at community pharmacies in New South Wales (NSW), Australia. METHODS: A multi-site cross-sectional survey design was utilised using a self-complete questionnaire. Participants were 508 clients receiving supervised methadone (n=442) and buprenorphine (n=66) at 50 community pharmacies. Participants were surveyed about whether they had diverted their currently prescribed pharmacotherapy, whether they had injected methadone or buprenorphine, the frequency, desirability and duration of action of injecting, and the ease of availability of street-purchased pharmacotherapies. RESULTS: The prevalence of recent diversion was more than 10 times higher among those receiving buprenorphine compared to methadone, with 23.8% of buprenorphine-maintained participants reporting diverting their dose in the preceding 12 months. Seventeen percent of methadone clients had injected methadone in the preceding 12 months compared with 9.1% of buprenorphine clients over the same time period. CONCLUSION: The higher prevalence of buprenorphine diversion compared to methadone diversion is likely to be due to its sublingual tablet formulation and difficulty associated with supervising its consumption compared to that of an oral liquid. Methadone diversion is also less prevalent likely due to the high levels of methadone take away provision, which also helps to explain the higher levels of recent methadone injecting compared to buprenorphine injecting. A clearer understanding of the motivations for diversion and injection of opioid pharmacotherapies, and the relationship between them is required.