Background: On the contrary that the reperfusion therapy for ST-segment elevation acute myocardial infarction is performed emergently, the invasive revascularization procedure for non-ST-segment elevation acute coronary syndrome (NSTE-ACS) could be delayed inappropriately, especially during weekends. We examined the effect of weekend admission on outcomes of NSTE-ACS patients. Methods: Patients who underwent percutaneous coronary intervention (PCI) for NSTE-ACS between 2008 and 2011 were enrolled and divided into ���weekends group��� and ���weekdays group��� depending on the timing of hospital visits. The 'weekends group' was defined as patients who visited hospital from Friday 6pm to Sunday 6pm. We compared the 30-day major adverse cardiac events (MACE) including cardiac death, recurrent myocardial infarction, and repeat revascularization in two groups. Results: A total of 265 patients (74.4% male) with NSTE-ACS (unstable angina/non-ST-segment elevation myocardial infarction 22.6%/77.4%) were enrolled and assigned to weekends group (n=97) and weekdays group (n=168). The 30-day MACE was significantly higher in weekends group than in weekdays group (5.2% vs 0.6%, P=0.026). The 30-day cardiac mortality was also significantly higher in weekends group (3.1 vs 0 %, P=0.048). Among contributing factors, visit-to-PCI time (median 41.1 vs. 25.7 hours, P<0.001), admission-to-PCI time (33.3 vs 19.7 hours, P<0.001), and duration of clopidogrel use before PCI (23.3짹23.7 vs 7.7짹14.9 hours, P=0.001) were significantly longer in weekends group. Baseline TIMI risk score was marginally higher in weekends group (3.1짹1.2 vs 2.8짹1.2, P=0.050). In multivariate analysis, weekend admission was the only significant predictor of the 30-day MACE (OR 40.1, 95% CI 2.968 – 542.145, P=0.005). The admission-to-PCI-time showed a trend toward an influence on the 30-day MACE (OR 1.162, 95% CI 0.994 -1.359, P=0.059). Conclusion: In patients with NSTE-ACS admitted to tertiary-care hospital and underwent PCI, admission on weekends was associated with higher occurrence of cardiac events. This might be due in part to in-hospital delay before PCI. Therefore, it seems to be important to establish system to perform urgent PCI as needed to patients with NSTE-ACS admitted on weekends.