After businesses realized the direct and indirect effect of suppliers on product quality, time-to-market, company's reputation; therefore, on their profit, purchasing function and supplier relationship management flourished in practice as well as in research. To manage purchasing function, gain competitive advantage, and enhance performance, supplier selection (SS) process should have appropriate methods and criteria for evaluating suppliers. The involvement of multi-criteria, several alternatives and decision-makers with different perspectives complicates the SS process. Therefore, this study proposes an extended use of the well-known TOPSIS method for solving a group decision-making problem under intuitionistic fuzzy (IF) environment in which all decision-makers' ideas are presented as IF values. The paper also aims to use IF numbers to explain the importance of alternatives and the weights of criteria. The application part of the paper focuses on selecting the best raw material supplier for a specific Turkish textile company by using ranking function.