BACKGROUND: Heart failure (HF) is a major global public health concern, particularly in older adults (aged ≥65 years). Despite its growing prevalence, comprehensive analyses of HF burden in this population, including trends, causes, and socioeconomic disparities, remain limited. METHODS: Using data from the Global Burden of Disease (GBD) Study 2021, we analyzed the burden of HF among older adults from 1990 to 2021, including prevalence, years lived with disability (YLDs), and underlying causes. We conducted a decomposition analysis to quantify the contributions of population growth, aging, and epidemiological changes and projected future trends to 2035 using Bayesian Age-Period-Cohort modeling. RESULTS: From 1990 to 2021, global HF cases among older adults increased from 14.1 million to 36.2 million, whereas YLDs rose from 1.34 million to 3.45 million. Population growth accounted for 89.0% of the increase in both prevalence and YLDs, while the aging effect varied by Sociodemographic Index (SDI) quintiles, , showing negative contributions (-39.4%) in high-SDI regions and positive contributions (+28.7%) in middle-SDI regions. Globally, ischemic heart disease was the leading cause of death (37.6%) across all SDI quintiles, followed by hypertensive heart disease (24.1%). The low-to-middle SDI regions experienced the fastest growth in HF burden (EAPC=0.22), with socioeconomic inequality widening over time. Projections suggest that age-standardized prevalence and YLDs will rise to 4,935 cases and 473 years lived with disability per 100,000 population, respectively, by 2035. CONCLUSIONS: Global heart failure burden in older adults is escalating fastest in low-middle SDI regions due to population growth and healthcare inequities. Mitigating this crisis requires prioritizing equitable access to evidence-based therapies and addressing socioeconomic disparities in aging populations.