The purpose of this study is to gain a better understanding of employee portal success and to identify the levers for its improvement. We introduce a theoretical model for this that is based on the DeLone and McLean IS Success Model, which considers the specific requirements of employee portals. We tested the associations between our model’s different success dimensions by using more than 4,400 employees’ responses. These responses were collected in a survey of twelve companies across different industries participating in an international benchmarking study. We applied structural equation modeling to carry out the causal analysis. Furthermore, within a performance-based analysis, we investigated the success dimensions’ improvement potentials from both a strategic and action-oriented perspective. The results of our causal analysis indicate that besides the factors contributing to the success of IS in general, other success dimensions – like the quality of the collaboration and process support – have to be considered when aiming for a successful employee portal. The performance-based analysis emphasizes the significance of collaboration quality to improve an employee portal and indentifies the respective fields of action. The study’s findings make it possible for practitioners to understand the levers with which to improve their employee portals and to prioritize their investments accordingly. By empirically validating a comprehensive success model for employee portals, the study's results advance the theoretical development in this area and present a basis for further research in this field.