Background: Acute stent thrombosis (STh) is a rare complication of percutaneous coronary intervention (PCI) and is associated with a high-risk of reperfusion failure. However, data focusing on risk factors of reperfusion failure in patients undergoing repeat PCI for treatment of STh remains inadequate. Methods: A total of 8815 patients who underwent PCI with stent implantation from January 2009 to December 2013 were retrospectively reviewed. Among those cases, patients that presented with acute STh and underwent a repeat PCI for acute STh were identified. Results: There were 108 patients who underwent repeat PCI for the treatment of in-hospital acute STh that were retrospectively analyzed. Of these study subjects, 21 (25%) had thrombolysis inmyocardial infarction (TIMI) flow < 3 after repeat PCI. The median value of pain-to-balloon time was 40 minutes in the TIMI < 3 group, 35 minutes in the TIMI = 3 group (p < 0.001), and the first PCI-to-stent thrombosis time was also longer in the TIMI < 3 group (10 hours vs. 2.5 hours, p = 0.001). When patients were evaluated according to PCI time, the percentage of patients with TIMI < 3 was significantly higher in the night period compared to the daytime period (46.4% vs. 17.5 %, p = 0.002). In the multivariable logistic regression analysis, stent length [odds ratio (OR) = 1.18, 95% confidence interval (CI) 1.008-1.38] and pain-to- balloon time (OR = 1.28, 95% CI, 1.06-1.54) were the only independent predictors of failed reperfusion. Conclusions: Baseline stent length and pain-to-balloon time were associated with reperfusion failure in PCI for STh. Moreover, TIMI flow grade showed a circadian variation.