Abstract Background Frailty is common in patients with heart failure (HF) and is associated with adverse outcome, but it is uncertain how frailty should best be measured. Objectives To compare the prognostic value of commonly-used frailty tools in ambulatory patients with HF. Methods and results We assessed, simultaneously, three screening tools [clinical frailty scale (CFS); Derby frailty index (DFI); acute frailty network (AFN) frailty criteria), three assessment tools (Fried criteria; Edmonton frailty score (EFS); deficit index (DI)) and three physical tests (handgrip strength, timed get-up-and-go test (TUGT), 5-metre walk test (5MWT)] in consecutive patients with HF attending a routine follow-up visit. 467 patients (67% male, median age = 76 years, median NT-proBNP = 1156 ng/L) were enrolled. During a median follow-up of 554 days, 82 (18%) patients died and 201 (43%) patients were either hospitalised or died. In models corrected for age, Charlson score, haemoglobin, renal function, sodium, NYHA, atrial fibrillation (AF), and body mass index, only log[NT-proBNP] and frailty were independently associated with all-cause death. A base model for predicting mortality at 1 year including NYHA, log[NT-proBNP], sodium and AF, had a C-statistic = 0.75. Amongst screening tools: CFS (C-statistic = 0.84); amongst assessment tools: DI (C-statistic = 0.83) and amongst physical test: 5MWT (C-statistic = 0.80), increased model performance most compared with base model (P <0.05 for all). Conclusion Frailty is strongly associated with adverse outcomes in ambulatory patients with HF. When added to a base model for predicting mortality at 1 year including NYHA, NT-proBNP, sodium, and AF, CFS provides comparable prognostic information with assessment tools taking longer to perform.