Diabetes mellitus has been increasingly recognized as a contributor to subclinical atrial dysfunction, particularly in hypertensive patients with preserved left ventricular ejection fraction. In our study, we demonstrated an association between diabetes and impaired left atrial mechanics assessed by two-dimensional speckle-tracking echocardiography. While the cross-sectional design does not allow causal inference, our findings support the hypothesis that diabetes may adversely affect atrial strain independent of overt cardiovascular disease. We adjusted for relevant clinical and echocardiographic variables, though residual confounding cannot be excluded. Patients with known atrial fibrillation were excluded, and although prolonged rhythm monitoring was not performed, this limitation reflects the real-world challenges of detecting silent paroxysmal arrhythmias. Echocardiography was chosen for its accessibility and widespread applicability, and reproducibility analyses confirmed good intra- and inter-observer agreement. Validation against other modalities such as cardiac magnetic resonance imaging was beyond the scope of the present study.