This is an evaluative study, with sequential explanatory mixed methods, aimed at evaluating the performance of the Brazilian Mobile Emergency Medical Service (SAMU) in the Grande ABC region, located in the state of São Paulo, Brazil. In the quantitative approach, an analysis of interrupted time series was performed to evaluate the immediate and gradual effects of the SAMU on hospital mortality due to acute myocardial infarction. The qualitative approach was conducted via semi-structured interviews and a thematic analysis was applied for the interpretation of the results, exploring the attitudes and values of the interviewees regarding the performance of SAMU in the Grande ABC region. Interrupted time series analysis showed a -0.04% reduction in the underlying mortality rate since SAMU implementation (95%CI: -0.0816; -0.0162; p-value = 0.0040) and a reduction in the mortality level, -2.89 (95%CI: -4.3293; -1.4623; p-value = 0.0001), both with statistical significance. To improve the robustness of the results, a control region was used, showing a statistically significant difference in the post-intervention result of -0.0639 (95%CI: -0.1060; -0.0219; p-value = 0.0001). The interviews revealed that the SAMU has the potential to intervene in the prognosis of transported cases, however, challenges related to the availability of beds, expansion of telemedicine, and continuous training of professionals for qualified emergency care in the event of a heart attack must be overcome. The results indicate that the studied intervention is part of a set of factors that, together, generate more conditions to achieve a better result.