Collaborative games will enable new kinds of possibilities for learning. In the future, the goal of game-based learning should be to introduce new ideas and deepen learners' in-depth understanding. However, studies have shown that shared high-level knowledge construction is a challenging process. Moreover, thus far, few empirical studies have examined what constitutes the teacher's role in games. The focus of this paper is to investigate teachers' real-time instructional activities in a scripted 3D game setting. The authors' hypothesis is that groups with real-time teacher instruction will come up with more shared knowledge construction that can be considered productive than groups studying without real-time teacher instruction. Thus, content analysis was conducted to compare collaboration processes between different learning conditions. This study indicates that the teacher has a special role in empowering collaborative knowledge construction in the 3D game context in vocational education. The authors' findings show that the teacher's participation in collaborative work helps groups to develop productive ways of providing knowledge and asking contextual questions. In addition, they illustrate the teacher's ability to involve students in formulating hypotheses, interpreting context, providing explanations and describing observations.