This work presents a system for an integrated evaluation of the implementation of small hydroelectric power plants (SHPs), based on a soft decision tree. The method generates the enterprise's sustainability index, where economic, environmental, and social aspects are considered in its interactions, with indicators measured in the field, sectoral indexes, and final index generated by fuzzy logic rule blocks. The methodology used to select the indicators and indexes followed four phases. First, a fuzzy expert system (FES) was developed in the form of a soft decision tree. Then, the array of suggested variables and weights were submitted to expert analysis using the Delphi methodology, and their assessments were collected. The third phase was the improvement of the system, taking into account the obtained considerations.In the fourth phase, the system was applied to a case study based on the installation of an SHP in the southern region of Brazil. The results obtained in the case study showed the sustainability of the enterprise. The presented method can have a significant contribution in supporting decisions regarding the licensing of hydroelectric projects.