IntroductionPrimary care provides an important opportunity to detect unhealthy alcohol use and offer assistance but many barriers to this exist. In an Australian context, Aboriginal Community Controlled Health Services (ACCHS) are community-led and run health services, which provide holistic primary care to Aboriginal and Torres Strait Islander peoples. A recent cluster randomised trial conducted with ACCHS provided a service support model which showed a small but significant difference in provision of ‘any treatment’ for unhealthy alcohol use. However, it was not clear which treatment modalities were increased.AimsTo test the effect of an ACCHS support model for alcohol on: (i) delivery of verbal alcohol intervention (alcohol advice or counselling); (ii) prescription of relapse prevention pharmacotherapies.MethodsIntervention: 24-month, multi-faceted service support model. Design: cluster randomised trial; equal allocation to early-support (‘treatment’) and waitlist control arms. Participants: 22 ACCHS. Analysis: Multilevel logistic regression to compare odds of a client receiving treatment in any two-month period as routinely recorded on practice software.ResultsSupport was associated with a significant increase in the odds of verbal alcohol intervention being recorded (OR = 7.60, [95% CI = 5.54, 10.42], p < 0.001) from a low baseline. The odds of pharmacotherapies being prescribed (OR = 1.61, [95% CI = 0.92, 2.80], p = 0.1) did not increase significantly. There was high heterogeneity in service outcomes.ConclusionsWhile a statistically significant increase in verbal alcohol intervention rates was achieved, this was not clinically significant because of the low baseline. Our data likely underestimates rates of treatment provision due to barriers documenting verbal interventions in practice software, and because different software may be used by drug and alcohol teams. The support made little impact on pharmacotherapy prescription. Changes at multiple organisational levels, including within clinical guidelines for primary care, may be needed to meaningfully improve provision of alcohol treatment in ACCHS.Trial registrationACTRN12618001892202 (retrospectively registered on 21/11/2018).