Background/Objectives: Acute heart failure (AHF) is a common cause of hospitalization in older adults, associated with high morbidity and mortality. In this population, frailty, comorbidity, and functional variability significantly influence prognosis. This study evaluated short-term (30-day) and long-term (1-year) mortality predictors in elderly patients with AHF treated in the emergency department (HED), considering clinical variables, comorbidities, and precipitating factors (PFs). Materials and Methods: An observational cohort study was conducted based on a secondary analysis of older patients with AHF included in the Epidemiology of Acute Heart Failure in Emergency Departments (EAHFE) registry, treated at Hospital Universitario Marqués de Valdecilla (HUMV) between 2007 and 2022. Clinical, laboratory, and PF-related variables were collected. The primary outcome was all-cause mortality at 30 days and 1 year. Univariate and multivariate logistic regression analyses were performed. Results: A total of 548 patients were included (mean age: 80.7 years), of whom 78.6% required hospitalization, mainly in the Internal Medicine department. Mortality was 11.1% at 30 days and 29.9% at 1 year. Age, valvular heart disease, dementia, and elevated creatinine levels were independently associated with higher mortality. Hypoxemia and low-output symptoms were linked to short-term mortality, while NYHA class III and anemia were associated with long-term mortality. Among PFs, acute coronary syndrome (ACS) was related to worse short-term outcomes, whereas rapid atrial fibrillation (AF) was inversely associated with long-term mortality. Conclusions: The prognostic relevance of risk factors differs between short- and long-term outcomes in older patients with AHF. Incorporating clinical characteristics and PFs into risk stratification models may support individualized management and guide follow-up strategies tailored to the geriatric profile. This multidimensional approach is essential to improve clinical decision-making and outcomes in a highly vulnerable population.