Floodwater spreading (FWS) is an important multi-objective technology in soil-water resources management, particularly to utilize excess runoff. More than 37 such schemes have been implemented in Iran. To measure the success of FWS projects, the factors influencing their performance is a prerequisite. Experienced professionals were asked to participate in a poll to identify the key factors that govern project success; a total of 50 researchers ultimately participated in the study. Seven factors were identified as key success factors governing the effectiveness of FWS in Iran. Fuzzy logic formalism was used to determine the success of FWS projects by integrating the factors into a single number that demonstrates the overall degree of success. Evaluation of the developed fuzzy index showed that the Tasuj FWS performed better than the other FWS projects investigated in 2009.