Aims: Mechanical complications (MC) (i.e., free wall rupture (FWR), papillary muscle rupture (PMR) and ventricular septal rupture (VSR)) are rare complications of ST- elevation acute myocardial infarction (STEMI). Incidence of MC according to pre-hospital delay remains unknown. We aimed to determine the rates of MC according to pre-hospital delay.Methods: Analysis was conducted on the MODIF registry data. Patients were allocated to four groups according to pre-hospital delay: 0 to 12 h, 12 to 24 h, 24 to 36 h and 36 to 48 h.Results: 6185 patients with complete data were analyzed. Mean age was 64.1 years old and 75.7% of patients were males. Eighty-three patients (1.34%) presented with MC: 44 (0.71%) experienced a FWR, 17 (0.27%) a PMR, and 22 (0.36%) a VSR. Global rates of MC were 0.82%, 1.43%, 1.24% and 5.07% in the four groups of pre-hospital delays - 0 to 12 h, 12 to 24 h, 24 to 36 h and 36 to 48 h - respectively (p < 0.001). In-hospital mortality rates were high: 44.2%, 47.1% and 54.6% for FWR, PMR and VSR, respectively. In multivariate analysis, factors independently related to the occurrence of MC were older age, female sex, simultaneous COVID-19 infection, absence of dyslipidemia, initial TIMI flow 0 or 1 in the culprit artery, 36 to 48 h-pre-hospital delay and absence of revascularization by percutaneous coronary intervention (PCI) with stent implantation.Conclusion: The probability of MC in STEMI increases with pre-hospital delay. Mechanical complications of STEMI remain associated with a very poor prognosis.