Increasing number of corporations applies IT service management systems to optimize IT service delivery and support processes. For this reason, implementation experiences and effect of IT service management system are growing concerns for IT managers and researchers. This case study analyzes implementation experiences on an ITIL based service management systems in an medium sized corporation. The exploratory case analysis revealed that systems and service quality were improved from the implementation. This study will contribute to the successful implementation of IT service management system and developing a research model of IT service management process.