Recently. interests in IT Service Management (ITSM) are increasing internationally as well as domestically. In order to realize the benefits from ITSM, it is necessary to institutionalize it as a culture of the organization through effective change management. One of the most promising approach of effective change management is a Six Sigma technique. In this study, we analyze a success case in which 6 Sigma was applied to Service Desk function which is one of the most important functions of ITSM. Through the analyses, this study aims to propose a feasible and specific approach to institutionalize ITSM. To accomplish the objective. the study analyzed specific methods of application of 6 Sigma to ITSM. performance of the project and future directions based on interview and project document/deliverable review. This study could not provide detailed performance measures due to lack of previous research on this topic and difficulty of obtaining quantitative data. However. this study has contributed to proposing a direction to institutionalize ITSM in organizations by analyzing a feasibility of 6 Sigma in implementing ITSM.