BACKGROUND: C5 palsy is a debilitating complication that may occur after posterior cervical decompression or fusion surgery, characterized by acute deltoid and biceps weakness. While most cases resolve spontaneously, prolonged dysfunction imposes significant physical, psychological, and socioeconomic burdens. Virtual reality (VR) has emerged as a promising adjunct in neurorehabilitation, offering immersive environments that promote engagement and motor learning. However, its application in postoperative C5 palsy rehabilitation remains underexplored. METHODS: This single-center randomized controlled trial was conducted from January to December 2023 at a tertiary academic hospital. Adult patients (≥ 20 years) who developed new-onset C5 palsy after posterior cervical fusion were enrolled. C5 palsy was defined as a ≥ 2-grade drop in shoulder flexion or abduction strength postoperatively. Patients were randomly assigned to either a control group that received standard postoperative rehabilitation or a VR-assisted group that received the same standard rehabilitation plus an additional VR-based rehabilitation program. VR rehabilitation included interactive, game-based shoulder exercises delivered via head-mounted displays during initial hospitalization and follow-ups at 3, 6, 12, and 24 weeks. Primary outcomes were surface electromyography-derived maximal voluntary isometric contraction (MVIC), %MVIC, and fatigue index (FI) of the deltoid muscles. Secondary outcomes included the Medical Research Council (MRC) scale, Neck Disability Index (NDI), EuroQoL-5 Dimension (EQ-5D), Visual Analog Scale (VAS), and Hospital Anxiety and Depression Scale (HADS). Data were collected preoperatively and at each postoperative visit. Ten patients (VR = 4, Control = 6) completed the study. RESULTS: Final analysis included data from 4 patients in the VR group and 6 patients in the control group. The VR group demonstrated significantly greater efficiency in muscle activation, evidenced by lower %MVIC values at 24 weeks during both shoulder flexion (median 1.0 vs. 1.5; p = 0.025) and abduction (0.9 vs. 1.8; p = 0.014). Improvements in patient-reported quality of life (EQ-5D, p = 0.032) and arm pain reduction (VAS, p = 0.048) were observed. Depression scores (HADS-D) and anxiety scores (HADS-A) also trended lower in the VR group, particularly at 24 weeks (HADS-D: 4.0 vs. 9.5; p = 0.067). Functional metrics, including maximum arm elevation (from 90.0 cm to 145.0 cm) and apple placement count (from 25 to 55 per session), improved markedly in the VR group. CONCLUSIONS: VR-assisted rehabilitation may contribute to improved neuromuscular efficiency, pain reduction, and psychological well-being in patients with postoperative C5 palsy. These preliminary findings suggest that immersive VR could be a promising adjunct in postoperative spinal rehabilitation, warranting further investigation in larger studies. TRIAL REGISTRATION: Clinical Research Information Service (CRIS), KCT0010436. Registered on April 21, 2025. Retrospectively registered.