Heart failure (HF) with preserved ejection fraction (HFpEF) is the most common form of HF in older adults. While manifest as distinct clinical phenotypes, almost all patients with HFpEF will present with exercise intolerance or exertional dyspnea. Distinguishing HFpEF from other clinical conditions remains challenging, as the accurate diagnosis of HFpEF involves integrating a diverse array of cardiovascular (CV) structural and physiologic inputs. Owing to its intrinsic ability to characterize the structure and function of the myocardium, cardiac valves, pericardium, and vasculature, echocardiography (TTE) has emerged as an essential modality for diagnosing HFpEF. In contrast to HF with reduced EF, however, no single TTE variable defines HFpEF. Abnormal diastolic function is typically associated with HFpEF, but "diastolic dysfunction" per se is not synonymous with "HFpEF": the pathophysiology of HFpEF is more complex than diastolic dysfunction alone. HFpEF may involve abnormalities at multiple loci within the CV system, including (1) dysfunction of the left ventricle, left atrium, or right ventricle; (2) pulmonary hypertension or pulmonary vascular disease; (3) pericardial restraint; (4) abnormal systemic vascular impedance; (5) coronary or peripheral microcirculatory dysfunction; and (6) defects of tissue oxygen uptake within the periphery. Thus, the accurate diagnosis of HFpEF - and its specific clinical phenotypes - requires diagnostic algorithms that comprise multiple clinical variables, many of which may be derived from TTE data. Refining such algorithms to better discriminate among specific HFpEF phenotypes is the subject of continued investigation.