IMPORTANCE: Preoperative anxiety is common among adult patients undergoing elective surgery and is associated with negative outcomes. Virtual reality (VR)-based interventions have been considered simpler, safer, and more effective for reducing anxiety in patients undergoing surgery than conventional care. OBJECTIVE: To examine the effectiveness of a VR-based intervention with preoperative education in reducing preoperative anxiety among adult patients undergoing elective surgery. DESIGN, SETTING, AND PARTICIPANTS: An assessor-blinded prospective randomized clinical trial was conducted to recruit adult patients aged 18 years or older who were scheduled for their first elective surgery procedure under general anesthesia within the next 2 to 4 weeks at a preanesthesia assessment clinic in Hong Kong from July to December 2022. INTERVENTIONS: Participants were randomly assigned to either an intervention group (an 8-minute immersive 360° VR video tour in the operating theater via a head-mounted display console) or a control group (standard care). MAIN OUTCOMES AND MEASURES: The primary outcome of preoperative anxiety was measured using the Amsterdam Preoperative Anxiety and Information Scale (range, 6-30; higher scores indicate greater anxiety), and the secondary outcomes (ie, stress, preparedness, and pain) were assessed by Visual Analog Scale at 3 time points: baseline at beginning of clinical session (T0), at the end of the clinical session immediately after the intervention (T1), and before the surgery (T2). Pain, satisfaction levels, and postoperative length of stay were evaluated after the surgery (T3). Simulation sickness was assessed after the intervention by use of the Simulation Sickness Questionnaire. A generalized estimating equations model was applied to compare changes in outcomes over time. RESULTS: A total of 74 participants (mean [SD] age, 46.34 [14.52] years; 38 men [51.4%] and 36 women [48.6%]) were recruited and randomized to the control group (37 participants) and intervention group (37 participants). Compared with the control group, the VR-based intervention group showed significantly decreased preoperative anxiety at T1 (β, -5.46; 95% CI, -7.60 to -3.32; P < .001) and T2 (β, -5.57; 95% CI, -7.73 to -3.41; P < .001), lower stress at T1 (β, -10.68; 95% CI, -16.00 to -5.36; P < .001) and T2 (β, -5.16; 95% CI, -9.87 to -0.45; P = .03), and higher preparedness at T1 (β, 6.60; 95% CI, 0.97 to 12.19; P = .02). Satisfaction levels were significantly increased in the intervention group vs the control group (mean [SD] score, 81.35 [9.24] vs 65.28 [8.16]; difference, 16.07; 95% CI, 12.00 to 20.15; P < .001). No significant differences in pain and postoperative length of stay were found. CONCLUSIONS AND RELEVANCE: The findings of this study suggest that a VR-based intervention is a feasible and effective way to reduce preoperative anxiety in adult patients undergoing elective surgery. Given the promising results of this study, further study in the form of large-scale, multicenter, randomized clinical trials with broader implementation is warranted. TRIAL REGISTRATION: Chinese Clinical Trial Registry Identifier: ChiCTR2100051690.