Objective: The aim of this study was to determine the effect of an ultrasound training course on the performance of emergency medical technicians (EMTs) in terms of using extended-focused assessment with sonography in trauma (E-FAST) in the pre-hospital setting. Methods: In this quasi-experimental study, 107 EMTs affiliated to Shahid Beheshti and Kashan Universities of Medical Sciences, were randomly selected. At first, the EMTs were given a pre-test of five images concerning normal and abnormal ultrasound views of thoracic and abdominal cavities. Then, 6 hours of theoretical and practical sessions were done by emergency medicine specialists to teach the EMTs to use ultrasound for the detection of pneumothorax and free fluid. The EMTs were tested again in the form of 18 images post-test as well as a 13-item survey to evaluate their skills in taking correct 10 E-FAST. Results: A total of 107 EMTs with the mean age of 27±15.21 and average of 3.5 years work experience participated in this study. The mean of test score increased from 0.57± 0.19 to 0.81±0.08 (with P < 0.001) out of the total score of 100. In the 4-graded survey, 98% of EMTs obtained good to excellent grades in working with ultrasound machine. Also, 50.5% of EMTs were good in taking Morison’s view and 46.6% and 45.6% had medium grades in pericardial and splenorenal views, respectively. In addition, 22.3% had weak grades in taking pericardial views. Conclusion: The results of the present study showed that the implementation of the training course significantly improved the accuracy of free fluid detection in thoracic and abdominal cavities by EMTs.