This paper presents a conceptual approach and a Web-based service that aim at supporting self-regulated learning in virtual environments. The conceptual approach consists of four components: 1) a self-regulated learning model for supporting a learner-centred learning process, 2) a psychological model for facilitating competence-based personalization and knowledge assessment, 3) an open learner model approach for visual interaction and feedback, and 4) a learning analytics approach for capturing relevant learner information required by the other components. The Web-based service provides a technical implementation of the conceptual approach, as well as a linkage to existing virtual environments used for learning purposes. The approach and service have been evaluated in user studies in university courses on computer science to demonstrate the usefulness of the overall approach and to get an understanding of some limitations.