Introduction: Sepsis is one of the main reasons for consultation at emergency departments. Objective: To identify the prevalence of sepsis in emergency departments of Mexico. Method: Cross-sectional study with a 30-day follow-up of patients diagnosed with sepsis or septic shock; demographic variables, management and outcomes were analyzed. Results: In 68 emergency departments analyzed, 2379 patients were attended to, out of whom 307 had sepsis. The prevalence of sepsis was 12.9 %, and overall mortality was 16.93 %, which in the cases of sepsis was 9.39 %, and in those of septic shock, 65.85 %; no significant differences were identified in demographic variables or type of hospital. A significantly higher fluid balance was observed within the first three hours in those patients who died, as well as a lack of adherence to international resuscitation recommendations. Conclusions: A high prevalence of sepsis was found in Mexican emergency departments. Mortality of patients with septic shock was similar and even higher than that internationally reported.