Late infarct size (IS) after ST segment elevation myocardial infarction (STEMI) is a determinant of subsequent mortality. Late Gadolinium enhancement in cardiac magnetic resonance imaging (LGE-CMRI) is the gold standard for IS measurement, however, it is not readily accessible in many areas. We aimed to evaluate the value of early baseline 2D-echocardiographic global longitudinal strain (GLS) for the prediction of late IS after STEMI. From October 2017 to July 2018, we studied 100 patients with their 1st anterior STEMI treated with primary percutaneous coronary intervention. Baseline GLS calculation was performed within 48 h of admission. In addition, the average value of the nine segments supplied by the LAD was assessed separately (anterior GLS). Infarct size was assessed 3 months later using LGE-CMRI, and large infarcts were defined as ≥ 20% LV myocardium covered by scar. Based on CMRI, we defined two groups; 57 patients with large infarcts (group I) and 43 patients with small infarcts (group II). Both groups were matched in all baseline demographics and risk factors. There was a good and significant correlation between GLS and late IS (r = − 0.840, P < 0.001). This correlation was even higher for anterior GLS (r = − 0.867, P < 0.001). ROC analysis showed a cut-off point of GLS (− 13%) that identified large late IS with a sensitivity and specificity of 66.7% and 88.4% respectively (AUC = 0.85). For anterior GLS, the cut-off point was − 9.6% (Sensitivity 94%, specificity 86%, AUC = 0.9). We concluded that baseline GLS significantly predicts late IS after anterior STEMI.