The importance of a service innovation as a result of increasing competition and customer demands in manufacturing firms has been widely recognized. Especially, a service innovation can be incorporated internally to sustain a firm' competitive advantage. In the context of manufacturing firms, this study investigates the triggering factors of an internal service innovation and its corresponding implementation strategy. This study adopts a multiple case studies method and examines the critical factors: internal user involvement and top management support. It is found the internal user involvement is neither the trigger nor significantly contributing to an internal service innovation's success. On the other hand, the topmanagement support is ascertained to be crucial for such a success; top-down approach is more likely to happen to implement the new internal service. Additionally, a new factor, economic freedom, is found to have a significant impact (positive) on an internal service innovation's success.Keywords -Internal service innovation, manufacturing firms, internal users, top management, economic freedom 978-1-4673-8066-9/15/$31.00 ©2015 IEEE Proceedings of the 2015 IEEE IEEM