Primary percutaneous coronary intervention (PPCI) is the optimal reperfusion strategy in patients with ST elevation Myocardial Infarction (STEMI). However, despite achieving TIMI 3 flow after PPCI, some patients have less optimal perfusion at the myocardial tissue level, as assessed by Myocardial Blush Grade (MBG) and consequently show adverse outcome. This prospective observational study was performed in the National Institute of Cardiovascular Diseases (NICVD), Dhaka, Bangladesh from March 2016 to February 2017. Total 74 patients with STEMI who underwent primary PCI and achieved TIMI 3 flow were included among them 37 patients were taken with low MBG (grade 0 or 1) in Group I and other 37 patients with high MBG (grade II or III) were taken in Group II. Mean age of Group I and Group II were 53.70±9.17 and 51.49±9.41 years respectively (p=0.536). Male to female ratio was 5.7:1. Smoking (59.5% versus 35.1%, p=0.036) and diabetes mellitus (43.2% versus 18.9%, p=0.024) were significantly higher in low MBG group than high MBG group. Multi vessel involvement (24.3% versus 5.4%, p=0.022) and anterior MI (72.9% versus 51.4%, p=0.047) were significantly higher in low MBG group. LVEF was significantly lower in low MBG group than high MBG group (49.92?6.60% versus 58.84?4.55%, p=0.003). Among the complications acute heart failure was found significantly higher in low MBG group than high MBG group (8.1% versus 0.0%, p=0.048) along with total adverse in hospital outcome (24.3% versus 5.4%, p=0.041). In study population total mortality was 2.7% and all were in low MBG group (5.4%). Multivariate logistic regression analysis showed MBG was an independent predictor of adverse in hospital outcome after PPCI (OR 6.553, 95% CI 1.984-21.643, p=0.002). Low MBG is associated with more adverse in hospital outcome after PPCI. So, along with TIMI 3 flow following PPCI we have to assess MBG for evaluation of complete reperfusion and further outcome.