Introduction: The Extended Focused Assessment with Sonography in Trauma (eFAST) protocol is an evaluation system that consists of ultrasonographic determination of intraabdominal free fluid, hemothorax, and pneumothorax. So far, there is no national research on this subject; in this context, the present study is proposed. Objectives: The general objective was to establish the diagnostic accuracy of the eFAST protocol performed by previously trained students and surgical residents in an emergency department. The obtained diagnosis was then compared to the intraoperative diagnosis, computed tomography (CT), or ultrasound. Methodology: A prospective, descriptive, observational study of diagnostic tests was performed. This study included patients who suffered a traumatic event involving kinetic energy transmission between January and September of 2022 and who were also submitted to an eFAST protocol in the Emergency Department of the Hospital de Clínicas in Montevideo, Uruguay. Results: Out of 100 eFAST protocols, 28 were performed by students and 72 by residents. No significant differences (p = 0.59) were found between operators. Of the 100 eFAST protocols, 69 were negative and 31 were positive (pneumothorax being the main diagnosis). CT was the most common comparison method (87%). This study met 70% sensitivity, 95% specificity, and 90% positive predictive value. The most frequent etiology was polytrauma (56%). Conclusion: The eFAST protocol performed by surgical residents and undergraduate students presented high specificity and high positive predictive value, with no significant differences between both groups. Clinical significance: This protocol has proven to be a valuable tool in the emergency department to improve patient prognosis. This is the first research to determine the diagnostic accuracy of said protocol at the national level, and the first to compare its precision between general surgery residents and previously trained advanced medical students.