Information system user satisfaction has been extensively documented as a key component and a surrogate of success and a determinant of individual and organizational performance. However, most related studies have focused on measuring user satisfaction and its impact through mathematical models, which might not exhaustively capture the issues affecting user satisfaction and performance. This study was conducted at the “Centre Hospitalier Universtaire de Kigali”, one of the two tertiary public and university teaching hospitals in Rwanda. This hospital has been implementing OpenClinic as an electronic medical record system since 2007, and few studies have focused on its evaluation. In addition, no study has focused on understanding the implications of user satisfaction for individuals’ work performance in this hospital. This study was cross-sectional mixed research using an explanatory embedded design. The data were collected from a convenient sample of OpenClinic users through questionnaires, which included closed- and open-ended questions, to capture both quantitative and qualitative data. The OpenClinic user satisfaction was high (91%), as was the proportion of users who perceived it as having a positive impact on their work performance (94%). The relationship between user satisfaction and perceived impact was statistically significant, and satisfied users were 20 times more likely to perceive that the impact was positive than unsatisfied users. Important concerns were expressed by users, and the main concerns were the poor functionality of the system due to unstable internet, the limited capacity for use and the scarcity of computers. Therefore, the implementation of the Electronic Medical Record system at the hospital has been successful, and user satisfaction has led to a perceived positive impact; however, further improvements are needed for optimal success. The inclusion of a qualitative component in future studies is recommended for a better understanding of IS success.