To compensate for the lack of funds for investment in private sector and infrastructure projects, governments may propose public–private partnerships (PPPs) to be able to use share capital and establish the necessary infrastructure of the country. The current study was undertaken to identify and determine the risk factors in PPPs for water supply projects in Iran. After identifying the risk factors using failure mode and effect analysis (FMEA), the risk priority number of each was assessed. This identified the most critical risk factors, which were then categorized into experimental, legal, financial, and technological subcategories. The fuzzy synthetic evaluation (FSE) technique and FMEA method were then blended and the FSE technique was modified for measuring the overall risk level. The computational results show that the levels of risk were ranked as follows (highest to lowest): financial, experimental, technological and legal. The level of risk in the financial subcategory was 6.11, in the experimental was 6.05 and in the technological and legal was 5.94 and 5.83, respectively. The overall risk level in PPPs for Iranian water supply projects considering linguistic variables as the criteria was 5.98, which is high. This level of risk confirms the applicability and suitability of the model.