Employee portals are collaborative information systems that are utilized by many companies to improve information exchange, communication, and employee collaboration, as well as to better support their business processes. Although some studies investigate single aspects of portal success, the critical success factors of how employee portals help their users become more productive have to date not been fully explored. To understand the antecedents of realizing employee performance gains though employee portals, we propose and validate a model of factors based on the human-computer interaction literature, particularly to better understand heterogeneity. Accordingly, we apply the finite mixture partial least squares (FIMIX-PLS) approach to uncover different segments of employee portal users and thereby provide a differentiated and more complete segment-specific picture of antecedents of employee portal utilitarianism. Our analysis indicates that the aggregate global model hides the existence of meaningful system user segments that are more homogenous in the productivity drivers. While some users are primarily concerned with ergonomicity, others users? productivity is the result of functionality. The future research steps we outline include the finding of exploratory variables that characterize different user groups and therefore further improve interpretability.