IntroductionAdverse drug events (ADEs) among hospitalised older adults are common yet often preventable. Efforts to recognise ADEs using pharmacist review and electronic health record adaptations have had mixed results. Our health system developed and implemented a geriatric prescribing context designed to offer age-friendly dose and frequency defaults for hospitalised patients 75 years and older. The impact of this context on ADEs remains unknown. To measure its impact, our team created a list of ADE-related International Classification of Diseases (ICD) codes specific to 10 commonly used medications at our institution. This protocol paper presents the process of designing a screening tool for ADEs, validating the tool with manual chart reviews and measuring the impact of the context on ADEs.Methods and analysisThis retrospective cross-sectional study will assess our list of ICD-10 codes against manual chart review to determine its accuracy. An electronic health record report for patients aged 75 years and older admitted to the hospital for a minimum of two nights was generated to identify 100 test positives and 100 test negatives. Test positives need at least one code from each level of our ICD-10 code list. The first level of codes identifies any possible ADEs while the second level is more symptom based. Test negatives must not have any code from the list. Two physicians blinded to test status will complete a structured chart review to determine if a patient had an ADE during their hospitalisation. Acceptable inter-rater reliability will need to be met before proceeding with independent chart review. Positive predictive value and negative predictive value will be calculated once all the chart reviews are completed.Ethics and disseminationThe Oregon Health & Science University Institutional Review Board approved this study (#21385). The results of the study will be disseminated in peer-reviewed journals and conference presentations.