Abstract: Six Sigma and lean manufacturing have always been presented as a novel organizational change and an improvement approach, especially as a mechanism for cost reduction in industry. The objective of the present research is to analyze the interrelationships of critical success factors of Lean Six Sigma (LSS) in industry. For this purpose, based on the review of the extant literature, 34 items were identified as the most important and pertinent critical success factors of LSS in industry and grouped into seven main factors. A questionnaire was later distributed to some 20 professors and experts in the field in order to analyze the interrelationships of the final listed factors. Eventually, a hybrid Grey-DEMATEL approach proposed to analyze the interrelationships of the factors. The Grey system theory was first appliedto represent the experts opinions under uncertainty and later the interrelationships of the critical success factors were analyzed using the DEMATEL method. The results of the analysis represent four metrics, namely (R), (D), (R+D) and (R-D) which stand for the effectiveness, influence, importance and cause/effect, respectively.