Background and aims: Construction industry is one of the riskiest industries all around the world and safety improvement in this industry is one of the main priorities in any country. A lot of researchers try to identify different factors that affect the safety. However, due to the large volume of high liquidity and volume of work in megaproject, identifying contributing factors to their safety is very important. So the main objective of this study was to identify and prioritize the factors affecting mega project in Iran.

Methods: In this study, by studying last researches, effective and different factors were identified. After that by using brainstorming session and Delphi, the most important parameters were chosen by experts. The hierarchical fuzzy method was used to prioritize the factors, therefore to weight the factors a total of 25 questionnaires were collected.

Results: At last attitude of the workers to safety issues, safety training and safety culture were detected as the most important factors that affect the safety performance of megaproject in Iran.

Conclusion: Due to identify the roles and attitudes of workers as the most important parameter affecting the performance of and safety in mega project, its reflects the importance of the selection of workers before entering the construction site. Although we cannot forbear the role of safety training, the best choice next to safety training is the selection of workers with a positive attitude towards safety.