The demand for green products have dramatically increased because the importance and public awareness of the preservation of natural environment was taken into consideration much more last two decades. As a result of this, especially manufacturing companies have been forced to design more green products, resulting in a problem of how they incorporate environmental issues into their design and evaluate concept options. The need for the practical decision making tools to address this problem is

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... pidly evolving due to the fact that the problem turns into a multiple-criteria decision making (MCDM) problem in the presence of a set of green concept alternatives and criteria. Therefore; in this paper, the four popular MCDM methods in fuzzy environment are utilized to reflect the vagueness and uncertainty on the judgments of DMs, because the crisp pairwise comparison in these conventional MCDM methods seems to be insufficient and imprecise to capture the right judgments of DMs. Of these methods; as Fuzzy AHP is used to calculate criteria weights, the other method; Fuzzy PROMETHEE II is used to rank alternatives. Furthermore, the incorporation of fuzzy set theory into these methods is discussed on a real-life case study.