Abstract Aims The EMPERIAL (Effect of EMPagliflozin on ExeRcise ability and HF symptoms In patients with chronic heArt faiLure) trials evaluated the effects of empagliflozin on exercise ability and patient-reported outcomes in heart failure (HF) with reduced and preserved ejection fraction (EF), with and without type 2 diabetes (T2D), reporting, for the first time, the effects of sodium-glucose co-transporter-2 inhibition in HF with preserved EF (HFpEF). Methods and results HF patients with reduced EF (HFrEF) (≤40%, N = 312, EMPERIAL-Reduced) or preserved EF (>40%, N = 315, EMPERIAL-Preserved), with and without T2D, were randomized to empagliflozin 10 mg or placebo for 12 weeks. The primary endpoint was 6-minute walk test distance (6MWTD) change to Week 12. Key secondary endpoints included Kansas City Cardiomyopathy Questionnaire Total Symptom Score (KCCQ-TSS) and Chronic Heart Failure Questionnaire Self-Administered Standardized format (CHQ-SAS) dyspnoea score. 6MWTD median (95% confidence interval) differences, empagliflozin vs. placebo, at Week 12 were −4.0 m (−16.0, 6.0; P = 0.42) and 4.0 m (−5.0, 13.0; P = 0.37) in EMPERIAL-Reduced and EMPERIAL-Preserved, respectively. As the primary endpoint was non-significant, all secondary endpoints were considered exploratory. Changes in KCCQ-TSS and CHQ-SAS dyspnoea score were non-significant. Improvements with empagliflozin in exploratory pre-specified analyses of KCCQ-TSS responder rates, congestion score, and diuretic use in EMPERIAL-Reduced are hypothesis generating. Empagliflozin adverse events were consistent with those previously reported. Conclusion The primary outcome for both trials was neutral. Empagliflozin was well tolerated in HF patients, with and without T2D, with a safety profile consistent with that previously reported in T2D. Hypothesis-generating improvements in exploratory analyses of secondary endpoints with empagliflozin in HFrEF were observed.