Heart failure (HF) with preserved ejection fraction (HFpEF) is a clinical syndrome in which patients have symptoms and signs of HF with normal or near-normal left ventricular ejection fraction (LVEF ≥50%). Roughly half of all patients with HF worldwide have an LVEF ≥50% and nearly half have an LVEF <50%. Thanks to the increased scientific attention about the condition and improved characterization and diagnostic tools, the incidence of HF with reduced ejection fraction (HFrEF) dropped while that of HFpEF has increased by 45%. HFpEF has no single guideline for diagnosis or treatment, the patient population is heterogeneously and inconsistently described, and longitudinal studies are lacking. To better understand and overcome the disease, in this review, we updated the latest knowledge of HFpEF pathophysiology, introduced the existing promising diagnostic methods and treatments, and summarized its prognosis by reviewing the most recent cohort studies.