A significant body of research has focused on the impact of immersive virtual reality (IVR) on vocabulary retention, but little is known about how to integrate language learning theories in IVR-mediated vocabulary learning. This study aims to examine the effect of IVR that integrate input processing model on vocabulary retention for elementary school students. A total of 77 fifth-grade students from elementary schools were recruited. They were randomly assigned to either an experimental group or a control group. The experimental group engaged with a vocabulary learning module delivered through IVR, while the control group received an equivalent module via PowerPoint (PPT). Vocabulary retention was assessed immediately after the intervention and at a delayed interval to gauge both short-term and long-term retention. The findings indicate that both IVR and PPT facilitate vocabulary retention; PPT appears to be more efficacious for immediate retention when compared to IVR; Conversely, IVR demonstrates a superior ability to enhance long-term vocabulary retention. These results suggest that the integration of language learning theory within IVR environments offer a significant advantage in vocabulary acquisition.