In this study, an exergame health-promoting system was implemented at a long-term care institution of patients with mental disorders. Through an evaluation of benefits of the system to institution residents and an examination of the system's service model, users' demands and the model limitations were identified serving as a paradigm for follow-up improvements of similar service models. The contextual inquiry of service experience engineering (SEE) was adopted to analyze the user-centered data of user service experiences regarding the exergame system. Five consolidated SEE models flow model, cultural model, sequence model, artifact model, and physical model were used to analyze the inadequacies of the current exergame service model. The potential users' demands were summarized and an affinity diagram was applied to propose the following suggestions for improving the innovative service model of the exergame system: (1) sufficient space at activity area: (2) personalization the difficulty of exergames; (3) a full- time staff member to assist in system operation and service delivery: (4) creating a pleasant atmosphere in the institution: (5) seeking budget subsidies actively. Mind mapping was also adopted to illustrate the relevance of those potential users' demands that did not show up in the affinity diagram. In summary, this study discussed user service experiences regarding an exergame system implemented at a long-term care institution of patients with mental disorders. The system service delivery model was examined by the contextual inquiry of SEE and mind mapping methods. The results can serve as a guideline for related institutions that intend to implement similar exergame systems.