Background Among factors which affect the outcome of rehabilitation after hip fracture, the role of pre-fracture frailty has not been defined. Objective To assess the impact of frailty on rehabilitation outcome in elderly persons with proximal hip fracture. Setting Geriatric rehabilitation center. Design Retrospective observational study. Subjects Forty consecutive patients with proximal hip fracture. Methods The following parameters were calculated: FI-MDS frailty index, Rockwood Clinical Frailty Scale (FI Rockwood), Functional Independence Measure (FIM) on discharge, absolute functional gain (ΔFIM), length of stay (LOS), and FIM gain per day (ΔFIM/LOS). FIM discharge ≥90 and motor FIM discharge >58 indicated success in rehabilitation. Results There were 31 women and 9 men, mean age 80 years. The mean pre-fracture FI MDS was 10 points (SD 5.8) out of 58 possible, the mean FI Rockwood score was 3 (SD 1.7) out of 7 possible. The mean admission FIM was 76.6 (SD 16), the mean discharge FIM was 92.7 (SD 19.3), mean LOS 22.5 days (SD 9.7), mean ΔFIM/LOS 0.8 (SD 0.6). Pre-fracture frailty was associated with worse outcome of rehabilitation: FI MDS predicted discharge FIM ≥90 with OR 0.86, p 0.012; FI Rockwood predicted discharge FIM ≥90 with OR 0.68, p 0.027; FI MDS predicted discharge motor FIM >58 with OR 0.91, p 0.07; FI Rockwood predicted discharge motor FIM >58 with OR 0.71, p 0.027. Conclusions Though pre-fracture frailty correlated with FIM on discharge, neither frailty tool was specific enough to predict success in rehabilitation and the necessary length of rehabilitation. Translating frailty scores in tools adequate for clinical decision making remains an aim for future studies.