Left ventricular end-diastolic pressure (LVEDP) is an independent predictor for prognosis in ST-elevation myocardial infarction (STEMI) patients. We aimed to investigate the relationship of admission LVEDP measured after a successful primary percutaneous coronary intervention (pPCI) with scintigraphic infarct size (IS) and global longitudinal strain (GLS), a strong predictor of IS, in STEMI patients. A total of 62 consecutive patients with STEMI were enrolled in the study. LVEDP measurements were performed after pPCI in patients who had TIMI-3 flow. Echocardiography was performed 24 h after pPCI and repeated 3 months later. GLS was calculated as an average peak strain from the 3 apical projections. IS was evaluated at the third month by technetium 99m sestamibi. The mean age was 56 ± 8 years in the study population. The mean LVEDP was found 19.4 ± 4.4 mmHg. Median IS was 4% (0–11.7 IQR).The mean GLS at the 24th hour and the third month were found to be − 15.4 ± 2.8 and − 16.7 ± 2.5 respectively. There was a moderate negative correlation between LVEDP and GLS (24th-hour p < 0.001 r = − 0.485 and third-month p < 0.001 r = − 0.489). LVEDP had a moderate positive correlation with scintigraphic IS (p < 0.001 r = 0.545). In the multivariable model, we found that LVEDP was significantly associated with scintigraphic IS (β coefficient = 0.570, p = 0.008) but was not associated with the 24th hour (β coefficient = 0.092, p = 0.171) and third month GLS (β coefficient = 0.037, p = 0.531). This study demonstrated that there was a statistically significant relationship between LVEDP and scintigraphic IS, and IS was increased with high LVEDP values. However, there was not a relationship between LVEDP and GLS.