There is concern whether patients with ST-segment elevation myocardial infarction (STEMI) who admitted to a percutaneous coronary intervention (PCI) center from interhospital transfer is associated with longer reperfusion time compared with direct admission. We evaluated the reperfusion delays in patients with STEMI who admitted to a primary PCI center through interhospital transfer or direct admission. We retrospectively analyzed 6,494 consecutive STEMI patients admitted between 2011 and 2019. Compared with direct admission (n = 4,121; 63%), interhospital transferred patients (n = 2,373) were younger (55 ± 10 vs. 56 ± 10 years, p < 0.001), had similar gender (85.6 vs. 86% male, p = 0.67), greater proportion of off-hour admission (65.2 vs. 48.3%, p < 0.001), less diabetes mellitus (28 vs. 30.8%, p = 0.019), and received more primary PCI (70.5 vs. 48.7%, p < 0.001). Interhospital transferred patients who received primary PCI (n = 3,677) or fibrinolytic (n = 238) had longer symptom-to-PCI center admission time (median, 360 vs. 300 minutes, p < 0.001), shorter door-to-device (DTD) time for primary PCI (median, 74 vs. 87 minutes, p < 0.001), and longer total ischemic time (median, 465 vs. 414 minutes, p < 0.001). Logistic regression in interhospital transferred patients showed that delay in door-in-to-door-out (DI-DO) time at the first hospital was strongly associated with prolonged total ischemic time (adjusted odds ratio = 3.92; 95% confidence interval: 3.06–5.04, p < 0.001). This study suggests that although interhospital transferred patients received more primary PCI with shorter DTD time, interhospital transfer creates longer total ischemic time that associates with the delay in DI-DO time at the first hospital that should be improved.