BACKGROUND: The prevalence of heart failure (HF) increases with age, and it is one of the leading causes of hospitalization and death in older patients. However, there are little data on in-hospital mortality in patients with HF ≥ 75 years in Spain. METHODS: A retrospective analysis of the Spanish Minimum Basic Data Set was performed, including all HF episodes discharged from public hospitals in Spain between 2016 and 2019. Coding was performed using the International Classification of Diseases, 10^th Revision. Patients ≥ 75 years with HF as the principal diagnosis were selected. We calculated: (1) the crude in-hospital mortality rate and its distribution according to age and sex; (2) the risk-standardized in-hospital mortality ratio; and (3) the association between in-hospital mortality and the availability of an intensive cardiac care unit (ICCU) in the hospital. RESULTS: We included 354,792 HF episodes of patients over 75 years. The mean age was 85.2 ± 5.5 years, and 59.2% of patients were women. The most frequent comorbidities were renal failure (46.1%), diabetes mellitus (35.5%), valvular disease (33.9%), cardiorespiratory failure (29.8%), and hypertension (26.9%). In-hospital mortality was 12.7%, and increased with age [odds ratio (OR) = 1.07, 95% CI: 1.07-1.07, P < 0.001] and was lower in women (OR = 0.96, 95% CI: 0.92-0.97, P < 0.001). The main predictors of mortality were the presence of cardiogenic shock (OR = 19.5, 95% CI: 16.8-22.7, P < 0.001), stroke (OR = 3.5, 95% CI: 3.0-4.0, P < 0.001) and advanced cancer (OR = 2.6, 95% CI: 2.5-2.8, P < 0.001). In hospitals with ICCU, the in-hospital risk-adjusted mortality tended to be lower (OR = 0.85, 95% CI: 0.72-1.00, P = 0.053). CONCLUSIONS In-hospital mortality in patients with HF ≥ 75 years between 2016 and 2019 was 12.7%, higher in males and elderly patients. The main predictors of mortality were cardiogenic shock, stroke, and advanced cancer. There was a trend toward lower mortality in centers with an ICCU.