Heart failure with preserved ejection fraction (HFpEF) has emerged as one of the most challenging and rapidly increasing cardiovascular syndromes worldwide. Despite normal or near-normal left ventricular ejection fraction, patients experience significant morbidity, reduced quality of life, and high mortality rates comparable to heart failure with reduced ejection fraction. Recent clinical evidence suggests that left ventricular diastolic dysfunction (LVDD) represents a pivotal pathophysiological substrate in the development of HFpEF. The early identification of diastolic abnormalities, therefore, plays a crucial role in preventing disease progression and improving long-term outcomes. This article reviews contemporary diagnostic approaches to early LV diastolic dysfunction, including echocardiographic markers, myocardial deformation imaging, and biomarker assessment. Particular emphasis is placed on the integration of Doppler echocardiography, tissue Doppler imaging, and speckle-tracking techniques in routine clinical practice. The clinical implications of early detection, therapeutic decision-making, and risk stratification are discussed. The findings underscore the importance of proactive screening strategies in high-risk populations to mitigate the global burden of HFpEF.