Six Sigma is a comprehensive quantitative improvement method that can achieve impressive results. The projectbased approach eliminates waste, reduces costs, increases profits, and improves organization quality. Project evaluation and selection are initial activities in implementing Six Sigma and are crucial in organizations. There are many studies available to help decision-makers handle the process of project selection, but in many decision-making problems, they have to make decisions with incomplete information and under uncertain situations. On the other hand, regarding the development of new concepts, such as sustainability and its role in achieving key outcomes, we used the concepts of the Perceptual Computer (Per-C) method. We proposed a model that incorporates the sustainability concept into project selection. In this model, we designed a Rule-based Computing With Words (CWW) engine according to the three stages of the Per-C method, the outputs of which are in the form of a recommendation. Finally, we used a real-world case to demonstrate the proposed model.