Background: One of the most important goals of health care organizations is measuring and improving the quality of health care and reduction of adverse events. Objectives: The aim of this study was to evaluate the degree of observance of the WHO surgical safety checklist at two hospitals in Tehran. Materials and Methods: During this analytic cross-sectional study the degree of observance and the effects of the checklist on patient outcomes were studied. The checklist was implemented at two teaching hospitals in Tehran, Iran. Results: One hundred patients (40 ± 15 years, 44 (44%) male and 56 (56%) female) were enrolled in our study. Determination of patients ‘ diagnoses, anesthesia safety check before anesthesia, patient connection to pulse oximetry, allergic airway disturbance check and aspiration risk, confirmation of patient identity, location of surgery and surgical method by surgeon and nurse, correct numbering of materials by nurse and correct ticketing by nurse were carried out in more than 90% of cases. Conclusions: In conclusion, our study demonstrated that surgery team members comply moderately to the WHO surgery safety checklist in Iran. Iranian health care providers need to show more adherence to some items of the checklist compared to their previous routine.