Received: May 2013, Accepted: March 2014 Background: Safety signs provide information as well as instructions concerning the hazard or dangers in the workplace. The correct comprehension of these signs is very important for doing the necessary feedback in the specific situation which are described. Materials and methods:In this descriptive study, the comprehension of 10 selected safety signs were investigated in 53 randomly selected employees of an industrial company in Shiraz. The comprehension test was carried out with the aid of a standard questionnaire obtained from ISO 9186-1:2007. Results: In this study the mean comprehension scores of the tested signs were 65.95 percent with standard deviation if 28.7. The highest and lowest comprehension scores were for "use hearing protectors" and "biological hazard" respectively. The comprehension of 40 percent of the tested safety signs was lower than the minimum acceptable values of ISO 3864 and ANSI Z535.3 standards. Conclusion: This study showed that there is a significant difference in comprehensions of tested safety signs. For full comprehension of safety signs it is necessary to train the employees or add supplementary texts to the symbols in some cases.