Objective: To evaluate the effect of advance trauma life support (ATLS®) training on general surgery residents clinical reasoning skills using the national boards-style objective structured clinical examination (OSCE).Methods: This cross-sectional single-center study was conducted in Shiraz University of Medical Sciences including 51 surgery residents that participated in a mandatory national board style OSCE between May 2014 and May 2015. OSCE scores of two groups of general surgery residents including 23 ATLS® trained and 28 non-ATLS® trained were compared using Mann-Whitney U test. The exam was graded out of 20 points and the passing score was ≥14 including 40% trauma cases.Results: There were 8(15.7%) women and 43(84.3%) men among the participants with mean age of 31.12 ± 2.69 and 33.67 ± 4.39 years in women and men respectively. Overall 7 (87.5%) women and 34 (79.07%) men passed the OSCE. The trauma section OSCE score was significantly higher in the ATLS® trained participants when compared to non-ATLS®(7.79 ± 0.81vs.6.90 ± 1.00; p=0.001). In addition, the total score was also significantly higher in ATLS® trained residents (16.07 ± 1.41 vs. 14.60 ± 1.40; p=0.001). There was no association between gender and ATLS® score (p=0.245) or passing the OSCE (p=0.503).Conclusion: ATLS® training is associated with improved overall OSCE scores of general surgery residents completing the board examinations suggesting a positive transfer of ATLS learned skills to management of simulated surgical patients including trauma cases.