Abstract: Objective To investigate the impact of preoperative frailty on 1-year all-cause mortality in elderly patients after hip fracture surgery. Methods Elderly patients with hip fractures, who were admitted to Changhai Hospital, Naval Medical University, between January 2018 and December 2023 were selected, and their clinical characteristics were retrospectively analyzed. The preoperative modified frailty index (mFI-5) was assessed, where frailty was defined as a preoperative mFI-5 score ≥2. A multivariable Cox proportional hazards regression model was used to evaluate the association between preoperative frailty and 1-year postoperative all-cause mortality, with subgroup analyses performed. Kaplan-Meier survival curves were plotted to compare survival differences between the groups. Results A total of 1,715 patients were included, of whom 158 (9.2%) died within 1 year after surgery. Multivariable Cox regression analysis showed that preoperative frailty was independently associated with an increased risk of 1-year all-cause mortality after surgery (HR=1.66, 95%CI=1.17-2.36, P=0.004). Kaplan-Meier survival curves showed that the frailty group had a higher 1-year postoperative mortality rate than the non-frailty group (P=0.009). Subgroup analyses indicated that the association between preoperative frailty and increased mortality risk was generally consistent across subgroups, with no significant interactions observed (P>0.05). Conclusions Preoperative frailty is an independent risk factor for 1-year all-cause mortality in elderly patients after hip fracture surgery. Preoperative frailty assessment may help identify high-risk patients early and provide reference for perioperative risk stratification and the development of targeted intervention strategies.