The authors sought to evaluate clinical outcomes of patients after an episode of acute heart failure (AHF) according to their adherence to the Mediterranean diet (MedDiet). It has been proved that MedDiet is a useful tool in primary prevention of cardiovascular diseases. However, it is unknown whether adherence to MedDiet is associated with better outcomes in patients who have already experienced an episode of AHF. We designed a prospective study that included consecutive patients diagnosed with AHF in 7 Spanish emergency departments (EDs). Patients were included if they or their relatives were able to answer a 14-point score of adherence to the MedDiet, which classified patients as adherents (≥9 points) or nonadherents (≤8 points). The primary endpoint was all-cause mortality at the end of follow-up, and secondary endpoints were 1-year ED revisit without hospitalization, rehospitalization, death, and a combined endpoint of all these variables for patients discharged after the index episode. Unadjusted and adjusted hazard ratios (HRs) were calculated. We included 991 patients (mean age of 80 ± 10 years, 57.8% women); 523 (52.9%) of whom were adherent to the MedDiet. After a mean follow-up period of 2.1 ± 1.3 years, no differences were observed in survival between adherent and nonadherent patients (HR of adherents HR  = 0.86; 95% confidence interval CI: 0.73 to 1.02). The 1-year cumulative ED revisit for the whole cohort was 24.5% (HR  = 1.10; 95% CI: 0.84 to 1.42), hospitalization 43.7% (HR  = 0.74; 95% CI: 0.61 to 0.90), death 22.7% (HR  = 1.05; 95% CI: 0.8 to 1.38), and combined endpoint 66.8% (HR  = 0.89; 95% CI: 0.76 to 1.04). Adjustment by age, hypertension, peripheral arterial disease, previous episodes of AHF, treatment with statins, air-room pulsioxymetry, and need for ventilation support in the ED rendered similar results, with no statistically significant differences in mortality (HR  = 0.94; 95% CI: 0.80 to 1.13) and persistence of lower 1-year hospitalization for adherents (HR  = 0.76; 95% CI: 0.62 to 0.93). Adherence to the MedDiet did not influence long-term mortality after an episode of AHF, but it was associated with decreased rates of rehospitalization during the next year.