Large and complex infrastructure projects, especially water and sewage projects, are always exposed to various internal and external risks. Risk management is very necessary for the successful completion of projects, therefore identifying and prioritizing project risks as part of the risk management process is important for project-oriented organizations. In order to assess the risk of projects, it is necessary to first identify the types of risks in projects. The risks were extracted using the data of previous researches as well as interviews with university professors and experts in the field of water and sewage, and the final selection of risks was done by screening through the Delphi method. Then, the cause and effect relationship between risks was discovered from the DEMATEL multi-criteria decision making methods and the identified risks were ranked through the ANP method. The results of this research showed that the ranking of risks based on the combination of DEMATEL and ANP methods in water and sewage projects respectively includes the risks of budgeting (G), monitoring and control (F) and human resources (H) in the first to third place and the risk of weather conditions. (J) is ranked ten. The results of this research are consistent with the results of some researches that have been done in the field of identifying and prioritizing the risks of water and sewage projects and the risk of dam construction projects.