Background: Pain and anxiety are significant issues in intensive care units. Virtual reality (VR) offers an immersive, interactive experience using mobile technology and 3D-enabled goggles, providing multisensory distraction that reduces anxiety and pain perception in critically ill patients. Objective: To determine the effect of smartphone-based immersive virtual reality on relieving pain and anxiety in critically ill patients. Design: A quasi-experimental research design was employed. Methods: A convenience sample of 120 critically ill patients was selected. Patients were equally assigned into two groups (intervention and control group). In the Intervention group, patients were subjected to virtual reality sessions, and in the control group, patients were subjected to deep breathing for relaxation technique as a traditional method. The intervention was done through a session that took 15 minutes at once. Patients' assessment was done by using the Numeric Rating Scale (NRS) and Hamilton Anxiety Rating Scale (HAM-A). Results: The mean pain and anxiety scores in the virtual reality intervention group decreased more than in the control group, with significant differences at different time intervals. Conclusion: VR therapy utilizing smartphones has positive effects in managing pain and anxiety in critically ill patients and it is recommended that critical care nurses should incorporate mobile-based immersive virtual reality as a novel method for pain relief.