AbstractObjectivesTo assess the effectiveness of a brief alcohol intervention for improving awareness of alcohol as a breast cancer risk factor, improving alcohol literacy, and reducing alcohol consumption by women attending routine breast screening.DesignSingle‐site, double‐blinded randomised controlled trial.SettingMaroondah BreastScreen (Eastern Health, Melbourne), part of the national breast cancer screening program.ParticipantsWomen aged 40 years or more, with or without a history of breast cancer and reporting any alcohol consumption, who attended the clinic for routine mammography during 5 February – 27 August 2021.InterventionActive arm: animation including brief alcohol intervention (four minutes) and lifestyle health promotion (three minutes). Control arm: lifestyle health promotion only.Major outcome measureChange in proportion of women who identified alcohol use as a clear risk factor for breast cancer (scaled response measure).ResultsThe mean age of the 557 participants was 60.3 years (standard deviation, 7.7 years; range, 40–87 years); 455 had recently consumed alcohol (82%). The proportions of participants aware that alcohol use increased the risk of breast cancer were larger at four weeks than at baseline for both the active intervention (65% v 20%; odds ratio [OR], 41; 95% confidence interval [CI], 18–97) and control arms of the study (38% v 20%; OR, 4.9; 95% CI, 2.8–8.8), but the change over time was greater for the active intervention arm (arm × time: P < 0.001). Alcohol literacy also increased to a greater extent in the active than the control arm, but alcohol consumption did not significantly change in either arm.ConclusionA tailored brief alcohol intervention for women attending breast screening was effective for improving awareness of the increased breast cancer risk associated with alcohol use and alcohol literacy more broadly. Such interventions are particularly important given the rising prevalence of risky drinking among middle‐aged and older women and evidence that even very light alcohol consumption increases breast cancer risk.RegistrationClinicalTrials.gov, NCT04715516 (prospective; 20 January 2021).