Methods: The present study was a cross-sectional study, conducted in 2014. The sample consisted of 180 employees in the National Petrochemical Company. They were selected according to the stratified random sampling method and responded to questionnaires about demographic characteristics, work situation awareness of Sneddon, Mearns, and Flin (2013), work stress of Cohen et al. (1983), and Epworth sleepiness scale. The data were analyzed by correlation coefficient and stepwise regression by using the SPSS 15. 

Results: The results showed that there were internal correlation among work stress, sleepiness, and work situation awareness. Also, the results of stepwise regression analysis revealed that work stress and sleepiness significantly predicted, respectively, almost 23% and 26% of variances of work situation awareness among workers. 

Conclusion: According to the findings of the present study, work stress and sleepiness can predict work situation awareness. Therefore, considering these variables can be important in promoting the awareness of work situation among workers.