Virtual contexts play a crucial role in assisting students' learning. Researchers have taken advantage of the potential of immersive virtual reality (VR) for situating students in inaccessible places, and for engaging them in learning activities. Meanwhile, several previous studies have reported that, in VR-based learning contexts, students' perception of immersion and learning motivation could be low owing to the lack of clear objectives and problem-solving scenarios. On the other hand, digital game-based learning is capable of enhancing students' engagement in a task. In this study, we designed a learning approach (namely RPG-VR) by means of integrating a role-playing game with VR technology to enhance students' science learning. Furthermore, a quasi-experiment was conducted to evaluate the students' learning effectiveness via, respectively, providing the RPG-VR learning approach and the conventional VR (called C-VR) learning approach for the experimental and control groups. The experimental results indicated that this approach significantly enhanced the students' perceptions of immersion, self-efficacy and extrinsic learning motivation, in comparison with the C-VR learning approach. Specifically, students who learned with the RPG-VR learning approach perceived more immersion in the engagement and the total immersion stages. This study contributes to existing knowledge of VR technology by providing that a digital role-playing game could reinforce the main characteristics of VR-based learning environments and enhance students' concentration on a learning task. However, no significant difference was found between the two groups in terms of promoting students' learning achievements, implying that more instructional assistance is needed to improve students' knowledge gains in VR-based learning environments.