Six-Sigma is a well-established and one of the most recognized approaches in manufacturing strategy development. Companies who have adopted and successfully implemented such a methodology were found to be more innovative which led to increased customer satisfaction and an improved bottom line. The aim of this study is to identify factors for successful Six-Sigma implementation by using the Analytic Hierarchy Process (AHP). The study involves four phases, which include: (1) assessment of potential factors and performance measures in Six-Sigma implementation (2) development of the problem structure and building the AHP model (3) soliciting and compilation of opinion on preferences through expert interviews, and (4) determination of critical success factors. Twenty-one experts, consisting of three-project champions and eighteen-black belts from five multinational companies located in Thailand, were interviewed. Expert Choice® software was used to compute the normalized and unique priority weights. The results of the data analysis determined the relative importance of individual factors, and in turn identified the critical factors on which organizations should consolidate their efforts in the process of implementing Six-Sigma methodology.