A protocol for a prospective observational cohort study to investigate the effect of frailty on long-term outcomes in older adults admitted with trauma. Patients aged 65 years and older admitted to the Severn Major Trauma Centre at North Bristol NHS Trust in England between November 2018 and September 2019, will be followed up at 4-years. The objective is to determine if there is an association between Clinical Frailty Scale and mortality at 4 years after admission to hospital with a traumatic injury. The primary outcome will be mortality as measured by time from hospital admission to death. Analyses will be adjusted for other factors shown to be associated with mortality, using a mixed-effects multivariable Cox proportional hazards model.