Background: Early percutaneous coronary intervention (PCI) is recommended for ST-segment elevation myocardial infarction (STEMI) treatment. Delays in time-to-PCI, kept within guideline recommendations, have seldom been investigated. Objectives: The purpose of this study was to investigate the consequences of delay, due to system factors or hospital distance, for the time between last patient distress call and PCI. Methods: Registry-based cohort study including times of first call to medical services, admission and PCI for patients admitted with STEMI in Copenhagen, Denmark (2014-2018). The main combined outcome included death, recurrent myocardial infarction, or heart failure estimated at 30 days and 1 year from event. Outcomes according to time from call to PCI (system delay) and door-to-balloon time were standardized to the STEMI population using multivariate logistic regression. Results: In total, 1,822 STEMI patients (73.5% male, median age 63.3 years [Q1-Q3: 54.6-72.9 years]) called the emergency services ≤72 hours before PCI (1,735, ≤12 hours). The combined endpoint of 1-year cumulative incidence was 13.9% (166/1,196) for patients treated within 120 minutes of the call and 21.2% (89/420) for patients treated later. Standardized 30-day outcomes were 7.33% (95% CI: 5.41%-9.63%) for patients treated <60 minutes, and 11.1% (95% CI: 8.39%-14.2%) for patients treated >120 minutes. Conclusions: The risk of recurrent myocardial infarction, death, and heart failure following PCI treatment of STEMI increases rapidly when delay exceeds 1 hour. This indicates a particular advantage of minimizing time from first contact to PCI.