Primary percutaneous coronary intervention (PCI) is the treatment of choice for patients with ST-elevation myocardial infarction (STEMI). We aimed to compare 1-month major adverse cardiac events (MACE) of patients undergoing primary PCI between 2 routine-hour and off-hour working shifts. In this cross-sectional study, 1791 STEMI patients were retrospectively evaluated who underwent primary PCI. The patients were classified into 2 groups of routine and off-hour according to the PCI start time and date [495 patients (27.7%) in routine-hour group; 1296 patients (72.3%) in off-hour group]. Cardiovascular risk factor, angiographic, procedural data, door-to-device time, and 1-month follow-up data of patients were compared between 2 groups. There was a statistical difference in door-to-device time between routine-hour and off-hour group [55 minutes (40-100 minutes) in off-hour group vs. 49 minutes (35-73 minutes) in routine-hour group; P ≤ 0.001]. However, most of the patients in both groups had door-to-device time ≤60 minutes. The frequency of 1-month MACE was 8.5% in off-hour group and 6.9% in routine-hour group (P = 0.260). After adjustment for possible confounders, the procedure result, in-hospital death, and 1-month MACE were not significantly different between both study groups. We found that STEMI patients treated with primary angioplasty during off-hour shifts had similar 1-month clinical outcomes to routine-hour shifts. Considering the high number of patients requiring primary PCI during off-hours, the importance of early revascularization in acute myocardial infarction, and the comparable clinical outcomes and procedural success, full-time provision of primary PCI services seems to be beneficial.