Background: The aim of this study was to assess the relation between pre-procedural N-terminal pro-B-type natriuretic peptide (NT-proBNP) and angiographic no-reflow phenomenon and improvement of left ventricular (LV) systolic function in patients who underwent primary PCI. Methods: We enrolled 163 patients (60.4짹11.4 years, male 79.7 %) with LV systolic dysfunction [defined as an echocardiographic LV ejection fraction (EF) <45 %] who underwent primary PCI for acute STEMI. The level of NT-proBNP was measured on admission and before PCI. Angiographic no-reflow after PCI was defined as TIMI flow grade <3. All patients with no-reflow received intracoronary injection of nicorandil and adenosine after no-reflow. The follow-up LVEF was measured at 9.1짹4.2 months after PCI. Results: The baseline characteristics between the groups with no-reflow group (n=55) and normal reflow group (n=92) are similar. The level of NT-proBNP was significantly higher in the no-reflow group than that in the normal reflow group (2879.9짹2198.2 vs. 1270.5짹 1627.8 pg/mL, p=0.022). The LVEF was improved more significantly in normal reflow group (42.5 to 52.9 % vs. 43.8 to 47.9 %, p=0.017). In no-reflow group, the group was divided according to LVEF recovery at follow up: LVEF recovery group (n=30) and LVEF no-recovery group (n=25). The baseline LVEF was similar between the groups (42.6짹2.2 vs. 40.1짹3.1 %, p=0.558), but at follow-up LVEF was significantly higher in LVEF recovery group compared with that in LVEF no-recovery group (51.5짹1.5 vs. 41.2짹5.6 %, p=0.007). The baseline NT-proBNP level was significantly higher in LVEF no-recovery group than that in LVEF recovery group (3209.3짹1946.6 vs. 1990.7짹862.3 pg/mL, p=0.048). In multivariate analyses, baseline NT-proBNP level was the independent predictor for angiographic no-reflow phenomenone (odds ratio, 4.04; 95% CI 1.33 to 12.28, p=0.014) and no-recovery of LVEF in patients with no-reflow (odds ratio, 3.24; 95% CI 1.01 to 10.43, p=0.013). Conclusion: Baseline NT-proBNP level is a strong predictor for development of no-reflow phenomenon and no-recovery of LVEF in acute STEMI patients who underwent primary PCI.