Background: the left atrium (LA) plays a major role in Left ventricular (LV) performance. LA function is a surrogate marker of LV diastolic dysfunction. LA mechanical dysfunction occurs in LV systolic and diastolic dysfunction, coronary artery disease, myocardial infarction (MI), hypertension, aortic stenosis and cardiomyopathies. In the MI process, the contribution of the LA to LV function may increase if the cardiac myocytes are not affected by direct ischemia. However, myocyte necrosis or ischemia of the LA or significant LV systolic/diastolic dysfunction affects this booster effect. Assessment of LA size and function provides prognostic data for the outcome of patients with MI or ischemia. Aim of the Study: was to evaluate LA function in patients with non-ST-segment elevation myocardial infarction (NSTEMI) by two-dimensional speckle tracking echocardiography (2D STE). Patient and Methods: 60 patients with NSTEMI and 20 age-matched normal control individuals were enrolled in this study. Conventional echocardiographic parameters and global longitudinal strain rate (GLSR) were measured at left ventricular (LV) and LA segments. Results: Compared with healthy subjects, patients with NSTEMI had significantly increased LA volumes but significantly decreased LA emptying fraction and GLSR. LA-GLSR had significant correlations with the 2D Doppler echocardiographic parameters of LA function. In particular, global LA peak negative strain rate during early ventricular diastole (LA-GLSRe) was significantly correlated with both LA 2D Doppler echocardiographic parameters and LV contractile function. This could be suggested as a better indicator to evaluate LA function as a preferred parameter of STE. Conclusion: It could be concluded that two-dimensional speckle tracking echocardiography represented a non-invasive, relatively simple and reproducible technique to assess left atrial myocardial function in patients with NSTEMI.