The ELECTRE I Multi-Criteria Decision-Making Method Based on Hesitant Fuzzy Sets Na Chen School of Economics and Management Southeast University, Nanjing, Jiangsu 211189, China School of Applied Mathematics Nanjing University of Finance and Economics Nanjing, Jiangsu 210023, China chenna njue@163.com Zeshui Xu * Business School, Sichuan University Chengdu 610064, P. R. China xuzeshui@263.net Meimei Xia School of Economics and Management Tsinghua University Beijing 100084, China meimxia@163.com Published 28 November 2013 Hesitant fuzzy set (HFS), which allows the membership degree of an element to a set represented by several possible values, is considered as a powerful tool to express uncertain information in the process of multi-criteria decision making (MCDM) problems. In this paper, we develop a hesitant fuzzy ELECTRE I (HF-ELECTRE I) method and apply it to solve the MCDM problem under hesitant fuzzy environments. The new method is formulated using the concepts of hesi- tant fuzzy concordance and hesitant fuzzy discordance which are based on the given score function and deviation function, and employed to determine the preferable alternative. Numerical examples are provided to demonstrate the application of the proposed method, and the in°uence of di®erent numbers of alternatives on outranking relations is analyzed based on a derived sensitive parameter interval in which a change in the parameters has no e®ects on the set of the nonoutranked alternatives. The randomly generated numerical cases are also investigated in the framework of the HF-ELECTRE I method. Furthermore, the outranking relations obtained in the HF-ELECTRE I method with those derived from the aggregation operator- based approach and the ELECTRE III and ELECTRE IV methods are discussed. Keywords: Hesitant fuzzy set; ELECTRE; multi-criteria decision making; hesitant fuzzy ELECTRE I; hesitant fuzzy concordance. 2000 Mathematics Subject Classi¯cation: 90B50, 91B06 *Corresponding author. International Journal of Information Technology & Decision Making Vol. 14, No. 3 (2015) 621–657 ° c World Scienti¯c Publishing Company DOI: 10.1142/S0219622014500187 621