Abstract Aims Recent data from national registries suggest that acute heart failure (AHF) outcomes might vary in men and women, however, it is not known whether this observation is universal. The aim of this study was to evaluate the association of biological sex and 1-year all-cause mortality in patients with AHF in various regions of the world. Methods and results We analysed several AHF cohorts including GREAT registry (22 523 patients, mostly from Europe and Asia) and OPTIMIZE-HF (26 376 patients from the USA). Clinical characteristics and medication use at discharge were collected. Hazard ratios (HRs) for 1-year mortality according to biological sex were calculated using a Cox proportional hazards regression model with adjustment for baseline characteristics (e.g. age, comorbidities, clinical and laboratory parameters at admission, left ventricular ejection fraction). In the GREAT registry, women had a lower risk of death in the year following AHF [HR 0.86 (0.79–0.94), P < 0.001 after adjustment]. This was mostly driven by northeast Asia [n = 9135, HR 0.76 (0.67–0.87), P < 0.001], while no significant differences were seen in other countries. In the OPTIMIZE-HF registry, women also had a lower risk of 1-year death [HR 0.93 (0.89–0.97), P < 0.001]. In the GREAT registry, women were less often prescribed with a combination of angiotensin-converting enzyme inhibitors and beta-blockers at discharge (50% vs. 57%, P = 0.001). Conclusion Globally women with AHF have a lower 1-year mortality and less evidenced-based treatment than men. Differences among countries need further investigation. Our findings merit consideration when designing future global clinical trials in AHF.