Introduction At least 10% of hospital admissions in high-income countries, including Australia, are associated with patient safety incidents, which contribute to patient harm (‘adverse events’). When a patient is seriously harmed, an investigation or review is undertaken to reduce the risk of further incidents occurring. Despite 20 years of investigations into adverse events in healthcare, few evaluations provide evidence of their quality and effectiveness in reducing preventable harm.This study aims to develop consistent, informed and robust best practice guidance, at state and national levels, that will improve the response, learning and health system improvements arising from adverse events.Methods and analysis The setting will be healthcare organisations in Australian public health systems in the states of New South Wales, Queensland, Victoria and the Australian Capital Territory. We will apply a multistage mixed-methods research design with evaluation and in-situ feasibility testing. This will include literature reviews (stage 1), an assessment of the quality of 300 adverse event investigation reports from participating hospitals (stage 2), and a policy/procedure document review from participating hospitals (stage 3) as well as focus groups and interviews on perspectives and experiences of investigations with healthcare staff and consumers (stage 4). After triangulating results from stages 1–4, we will then codesign tools and guidance for the conduct of investigations with staff and consumers (stage 5) and conduct feasibility testing on the guidance (stage 6). Participants will include healthcare safety systems policymakers and staff (n=120–255) who commission, undertake or review investigations and consumers (n=20–32) who have been impacted by adverse events.Ethics and dissemination Ethics approval has been granted by the Northern Sydney Local Health District Human Research Ethics Committee (2023/ETH02007 and 2023/ETH02341).The research findings will be incorporated into best practice guidance, published in international and national journals and disseminated through conferences.
