Background and Aim: Initial care of traumatic patients is important in reducing mortality rate and trauma-related complications. The Advanced Trauma Life Support (ATLS) course provides basic care standards for these patients. Methods: In this descriptive-analytic study, 55 nurses working in the emergency department of a teaching hospital in the city of Arak, Iran participated in a 4-day training program in winter 2017. On the first day, knowledge of the emergency nurses on the type of procedures, sequence of procedures and performance of procedures while dealing with a simulated traumatic patient was assessed through an objective structured clinical examination (OSCE) test. The ATLS training workshop was held for the second and third days and the same test as that of the first day was given to the same participants on the fourth day and the scores acquired on these two tests were compared. Results: The scores of the nurses after training in ATLS significantly increased in all three dimensions of the test compared to those before training (P <0.05). Compared to the first day, Knowledge of the participants of diagnostic procedures and their sequence and performance skill when dealing with stimulated traumatic patients significantly increased on the fourth day after training in ATLS (P <0.001). Conclusion: According to the findings of this study, providing all medical staff involved in trauma care with ATLS courses, especially simulated-based ones, can increase their knowledge and skills in dealing with these patients.