Introduction Antibiotic overuse in residential aged care (RAC) contributes to resident harm and antimicrobial resistance. Low-cost behavioural science interventions are effective in other settings but have not been trialled in RAC. As part of the National Aged Care Medication Roundtable, and in partnership with RAC providers, we co-developed a behavioural science intervention to reduce antibiotic use, along with an evaluation strategy. This presentation will describe the intervention, trial design, implementation challenges and progress to date. Methods The Smarter, Shorter, Safer intervention bundle consists of social norm feedback, public commitment and consumer information. A stepped-wedge cluster randomised controlled trial (SWCRCT) with a process evaluation is underway in 46 RAC homes. The trial will assess: the intervention’s effect on antibiotic use, sustainability of effects 6 months post-intervention, and stakeholder experiences over time. The SWCRCT includes three quarterly steps and all homes will receive the intervention three times. Outcomes include days of therapy (DOT)/1000 days, the percentage of antibiotics courses exceeding guideline duration, and the percentage of residents on an antibiotic. Qualitative interviews will explore stakeholder engagement with the intervention. Results The trial commenced in October 2025 and will conclude in Dec 2026. At baseline, mean systemic antibiotic use was 82.2 DOT/1000 days (range: 36.8 to 135.6 DOT/1000 days, with risk adjustment). Implementation challenges have included data structure changes and RAC staff turnover. Interviews with staff indicate positive, but also highlight barriers. Conclusion This trial will provide new evidence on the effectiveness and durability of a behavioural-science informed intervention to reduce antibiotic use in RAC, offering a scalable approach with modest resources requirements.