BACKGROUND: Mortality subsequent to a hospitalisation for heart failure is reported to be much lower in Japan than in the United Kingdom (UK). This could reflect differences in disease severity or in management. Accordingly, we directly compared patient backgrounds and outcomes between Japan and UK. METHODS: Consecutive patients admitted to academic hospitals in the UK and Japan with heart failure had a common set of variables, including plasma concentrations of N-terminal pro-B-type natriuretic peptide (NT-proBNP), collected during admission. Mortality during hospitalisations, at 90 and 180 days was recorded and stratified by quintile of NT-proBNP. RESULTS: Overall, 935 patients were enrolled; 197 from UK and 738 from Japan. Median (interquartile range) age [UK: 78 (71-88) vs. Japan: 78 (70-84) years; p = 0.947], glomerular filtration rate [UK: 49 (34-68) vs. Japan: 49 (33-65) ml/min/1.73 m2; p = 0.209] and plasma NT-proBNP [UK: 4957 (2278-10,977) vs. Japan: 4155 (1972-9623) ng/l; p = 0.186] were similar, but systolic blood pressure was lower in the UK [118 (105-131) vs. 137 (118-159) mmHg; p < 0.001]. Patients with a higher plasma NT-proBNP had a worse prognosis in both countries; in-hospital and post-discharge mortality rates were higher in the UK even after adjusting for prognostic variables including NT-proBNP. CONCLUSIONS: This analysis suggests that either unobserved differences in patient characteristics or differences in care (formal or informal) rather than greater heart failure severity may account for the worse outcome of heart failure in the UK compared to Japan.