Objective:The aim of this study is to modify the World Health Organization (WHO) Surgical Safety Checklist in order to be compatible to a hospital in Iran and measure effect of implementing this checklist on postoperative complications.Methods:In a cross-sectional study the views of surgeons and anesthesiologists of the main teaching hospital in Tabriz -Imam Reza Hospital- were taken by a form attached to the main checklist. The participants in this study asked to write their opinions on each item of checklist based on the environment of the hospital. Then, we performed before-after study to determine effect of a modified checklist implementing on postoperative complications.Results:Surgeons and anesthesiologists had consensus on 15 of 19 items of checklist to remain the same and just 4 items recommended to be changed. In pre intervention period of study, 100 patients (51 males and 49 females) were enrolled with the mean age of 48.5±13.5 years. The number of patients in the post intervention period was the same, but 49 males and 51 females, the mean age was 47.5 ±14.6 years. The incidence of any complications in pre intervention period was 30%, but this rate in post intervention period was 12% and the difference between 2 periods of study was statistically significant (p=0.002).Conclusion:World Health Organization Surgical Safety Checklist is better to modify based on the local needs and facilities in each hospital. After implementing of a modified surgical safety checklist, complications decreased by 58%.