###### Abstract  
With its ability to afford immersive and interactive learning experiences, virtual reality has been widely used to support experiential learning, of which the learning effectiveness is promoted by the instructional component of debriefing. The current literature on debriefing mainly focuses on the traditional learning contexts while little is known on its effectiveness in immersive virtual reality (IVR) learning environments. Based on the theories of experiential learning and debriefing, this study designed a debriefing strategy based on simulated learning experience and investigated its effectiveness on knowledge and behavioral learning in an IVR learning program, using a randomized controlled trial with 77 elementary students from Hubei province in China. The study results support the efficacy of IVR on improving knowledge acquisition and behavioral performance, and reveal a significant moderating effect of debriefing on the effectiveness of IVR learning environments. The study confirms the critical role of debriefing in IVR-based instruction and provides theoretical and practical implications for the design and implementation of effective IVR learning environments. virtual reality; debriefing; instructional design; learning outcomes; experimental design 2021110426. 11.10426. 11. 2019 and found that the overall learning effect of IVR (Hedge's \(g\)) was 0.24, which was smaller than the overall effect of DVR (\(g\) = 0.41-0.51) [12]; [PERSON] et al. (2021) reached a similar conclusion through meta-analysis of 149 experimental studies [2]. One possible reason for this phenomenon is that IVR isolates learners from physical reality completely, which causes a lack of interaction with teachers and peers during the learning process, and is, thus, not conducive to the deployment of teaching strategies. Compared with the technical affordances of IVR, the selection and application of proper teaching strategies play a more critical role in improving the effectiveness of IVR-based instruction [12]. Debriefing is a simple and easy-to-use teaching strategy that can potentially improve the learning effect of IVR. This strategy guides learners to recall, analyze, and evaluate their own or others' behavioral decisions in virtual scenarios through visualized and shared cognitive processes, thereby promoting reflective learning and knowledge construction in experiential learning [13]. Debriefing is widely practiced in military training and medical education, and has achieved positive learning results. For example, [PERSON] et al. (2015) showed that listening to experienced military personnel's reflective reports before conducting military training and rescue operations could increase trust and understanding among team members [14]; [PERSON] et al. (2018) revealed that one-on-one debriefing after simulation training obtained better results in subsequent medical knowledge tests [15]. In recent years, researchers have applied debriefing strategies in various educational contexts, including teacher training [16], transnational cultural education [17], and psychological therapy [18], and have reported significantly improved learning outcomes. However, most debriefing strategies described in the literature were implemented in traditional classrooms [19] with non-immersive simulation interventions [15; 16], with adults such as college students and corporate workers as target learners [16]. There is a lack of rigorous empirical evidence concerning whether or not the debriefing strategy is also applicable to the IVR learning environment, whether it can improve the learning performance of younger learners, and to what extent. In summary, informed by the experiential learning theory, IVR-based instruction has the potential to improve students' learning performance and experience. However, the current literature of VR-based instruction suffers from three limitations.