•The study compared six frailty tools in older hypertensive outpatients.•Frailty predicted 1-year functional decline, independently of baseline function and comorbidities.•The CFS (score ≥4) predicted 1-year decline with 91 % negative predictive value.•CFS may help identify non-frail hypertensive patients at low risk of functional decline. Few studies have evaluated frailty in older hypertensive individuals and the most appropriate tools to identify frailty in this population have yet to be identified. This study compared the performance of six frailty instruments in the prediction of 1-year functional decline in older hypertensive outpatients. The HYPERtension and FRAILty in Older Adults (HYPER-FRAIL) longitudinal pilot study involved hypertensive participants ≥75 years from two geriatric outpatient clinics at Careggi Hospital, Florence, Italy, undergoing identification of frailty with four frailty scales (Fried Frailty Phenotype, Frailty Index FI, Clinical Frailty Scale CFS, Frailty Postal Score) and two physical performance tests (Short Physical Performance Battery SPPB and gait speed). Prediction of 1-year functional decline (i.e. a ≥ 10-point Barthel Index decrease between baseline and follow-up) was examined based on ROC curve analysis and multivariable logistic regression. Among 116 participants, 24 % reported functional decline. In the ROC curve analyses, FI (AUC=0.76), CFS (AUC=0.77), gait speed (AUC=0.73) and the SPPB (AUC=0.77) achieved the best predictive performance, with FI ≥0.21 and CFS ≥4 showing the highest sensitivity (82 %) and negative predictive value (91 %). Frailty identified with FI, CFS or physical performance tests was associated with an increased risk of 1-year functional decline, independently of baseline functional status and comorbidity burden. FI, CFS and physical performance tests showed similar predictive ability for functional decline in hypertensive outpatients. The CFS and gait speed might be more suitable for clinical use and may be useful to identify non-frail individuals at lower risk of functional decline.