Abstract Background Acute myocardial infarction (AMI) remains a leading cause of morbidity and mortality worldwide. The effective management of patients with AMI is directly linked to time, and approximately one-half of the deaths attributed to AMI occur from cardiac arrest in the out-of-hospital setting, reinforcing the importance of the prehospital care. Contemporary data remain particularly lacking about the use of prehospital care in the setting of AMI, particularly from the more generalizable perspective of a community-based investigation, as well as information about the hospital outcomes of patients transported by ambulance. Purpose To assess the impact the implementation of a nationwide ambulance service (Serviço de Atendimento Médico de Urgência, SAMU) on AMI mortality and number of hospitalizations, in the state of Minas Gerais, Brazil. Methods Retrospective, ecological study, which assessed data from the Brazilian Universal Health System (SUS), from all 853 municipalities of Minas Gerais, from 2008 to 2016. SAMU implementation dates were obtained from the state government and SAMU local coordinators. Data on the population of each municipality was obtained from Instituto Brasileiro de Geografia e Estatística (IBGE), the Brazilian official demographic institute. Excessive skewness of general and in-hospital mortality rates were smoothed using the Empirical Bayes method The relationship between SAMU care in each municipality and the mortality due to AMI in the general population, in-hospital mortality and number of hospitalizations for AMI was assessed using the Poisson hierarchical model, and the analyzed rates were corrected by the age structure and detrended by seasonal influences. Results AMI mortality rates showed a decreasing tendency throughout the study, on average 2% per year, and seasonal variation, being higher during winter months. Age-corrected AMI in-hospital mortality also showed a decreasing trend, from 13.81% in 2008 to 11.43% in 2016. SAMU implementation was associated with decreased AMI mortality (odds ratio [OR]=0.967, 95% confidence interval [CI] 0.936–0.998) and AMI in-hospital mortality (OR=0.914, 95% CI 0.845–0.986) with no relation with the number of hospitalizations (OR 1.003, 95% CI 0.927–1.083). There was no seasonal variation in the number of AMI hospitalizations. Conclusion SAMU implementation was related to a modest but significant decrease in AMI in-hospital mortality. This finding reinforces the main role of prehospital care in AMI care and reinforces the need for investment in improving the service throughout the country.