BACKGROUND The efficacy of telemedicine in reducing delay times and short-term adverse clinical outcomes in patients with ST segment elevation myocardial infarction (STEMI) during the coronavirus disease 2019 (COVID-19) pandemic is unclear. This study compared outcomes in patients with STEMI who had percutaneous coronary intervention (PCI) and the use of a telemedicine app from August 2019 to March 2020 at a single center in Beijing, China. MATERIAL AND METHODS A total of 243 patients with STEMI who underwent PCI were consecutively enrolled and divided into 2 groups according to the date, before or after the pandemic. The 2 groups were further divided into patients who used the app for consulting and those who did not. RESULTS The time from symptom onset to calling an ambulance (SCT), door to balloon time (DTB), and total ischemia time (TIT) were significantly prolonged in patients after the pandemic. Patients who used the app had shorter SCT, DTB, and TIT before and after the pandemic compared to those who did not. Adverse clinical outcomes were significantly higher after compared with before the pandemic, despite the incidence rate of stroke, any revascularization, and stent thrombosis. However, there was no significant difference in short-term adverse clinical outcomes between patients who used the app and those who did not before and after the pandemic. CONCLUSIONS Telemedicine reduced the delay time of STEMI patients during the COVID-19 pandemic. The difference in short-term adverse clinical outcomes was not statistically significant between patients who used the app and those who did not.